Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4974 insertions, 0 deletions

diff --git a/tools/profiler/tests/gtest/GeckoProfiler.cpp b/tools/profiler/tests/gtest/GeckoProfiler.cpp
new file mode 100644
index 0000000000..1bf70bce09
--- /dev/null
+++ b/tools/profiler/tests/gtest/GeckoProfiler.cpp
@@ -0,0 +1,4974 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file tests a lot of the profiler_*() functions in GeckoProfiler.h.
+// Most of the tests just check that nothing untoward (e.g. crashes, deadlocks)
+// happens when calling these functions. They don't do much inspection of
+// profiler internals.
+
+#include "mozilla/ProfilerThreadPlatformData.h"
+#include "mozilla/ProfilerThreadRegistration.h"
+#include "mozilla/ProfilerThreadRegistrationInfo.h"
+#include "mozilla/ProfilerThreadRegistry.h"
+#include "mozilla/ProfilerUtils.h"
+#include "mozilla/ProgressLogger.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#include "nsIThread.h"
+#include "nsThreadUtils.h"
+#include "prthread.h"
+
+#include "gtest/gtest.h"
+#include "mozilla/gtest/MozAssertions.h"
+
+#include <thread>
+
+#if defined(_MSC_VER) || defined(__MINGW32__)
+#  include <processthreadsapi.h>
+#  include <realtimeapiset.h>
+#elif defined(__APPLE__)
+#  include <mach/thread_act.h>
+#endif
+
+#ifdef MOZ_GECKO_PROFILER
+
+#  include "GeckoProfiler.h"
+#  include "mozilla/ProfilerMarkerTypes.h"
+#  include "mozilla/ProfilerMarkers.h"
+#  include "NetworkMarker.h"
+#  include "platform.h"
+#  include "ProfileBuffer.h"
+#  include "ProfilerControl.h"
+
+#  include "js/Initialization.h"
+#  include "js/Printf.h"
+#  include "jsapi.h"
+#  include "json/json.h"
+#  include "mozilla/Atomics.h"
+#  include "mozilla/BlocksRingBuffer.h"
+#  include "mozilla/DataMutex.h"
+#  include "mozilla/ProfileBufferEntrySerializationGeckoExtensions.h"
+#  include "mozilla/ProfileJSONWriter.h"
+#  include "mozilla/ScopeExit.h"
+#  include "mozilla/net/HttpBaseChannel.h"
+#  include "nsIChannelEventSink.h"
+#  include "nsIThread.h"
+#  include "nsThreadUtils.h"
+
+#  include <cstring>
+#  include <set>
+
+#endif  // MOZ_GECKO_PROFILER
+
+// Note: profiler_init() has already been called in XRE_main(), so we can't
+// test it here. Likewise for profiler_shutdown(), and AutoProfilerInit
+// (which is just an RAII wrapper for profiler_init() and profiler_shutdown()).
+
+using namespace mozilla;
+
+TEST(GeckoProfiler, ProfilerUtils)
+{
+  profiler_init_main_thread_id();
+
+  static_assert(std::is_same_v<decltype(profiler_current_process_id()),
+                               ProfilerProcessId>);
+  static_assert(
+      std::is_same_v<decltype(profiler_current_process_id()),
+                     decltype(baseprofiler::profiler_current_process_id())>);
+  ProfilerProcessId processId = profiler_current_process_id();
+  EXPECT_TRUE(processId.IsSpecified());
+  EXPECT_EQ(processId, baseprofiler::profiler_current_process_id());
+
+  static_assert(
+      std::is_same_v<decltype(profiler_current_thread_id()), ProfilerThreadId>);
+  static_assert(
+      std::is_same_v<decltype(profiler_current_thread_id()),
+                     decltype(baseprofiler::profiler_current_thread_id())>);
+  EXPECT_EQ(profiler_current_thread_id(),
+            baseprofiler::profiler_current_thread_id());
+
+  ProfilerThreadId mainTestThreadId = profiler_current_thread_id();
+  EXPECT_TRUE(mainTestThreadId.IsSpecified());
+
+  ProfilerThreadId mainThreadId = profiler_main_thread_id();
+  EXPECT_TRUE(mainThreadId.IsSpecified());
+
+  EXPECT_EQ(mainThreadId, mainTestThreadId)
+      << "Test should run on the main thread";
+  EXPECT_TRUE(profiler_is_main_thread());
+
+  std::thread testThread([&]() {
+    EXPECT_EQ(profiler_current_process_id(), processId);
+
+    const ProfilerThreadId testThreadId = profiler_current_thread_id();
+    EXPECT_TRUE(testThreadId.IsSpecified());
+    EXPECT_NE(testThreadId, mainThreadId);
+    EXPECT_FALSE(profiler_is_main_thread());
+
+    EXPECT_EQ(baseprofiler::profiler_current_process_id(), processId);
+    EXPECT_EQ(baseprofiler::profiler_current_thread_id(), testThreadId);
+    EXPECT_EQ(baseprofiler::profiler_main_thread_id(), mainThreadId);
+    EXPECT_FALSE(baseprofiler::profiler_is_main_thread());
+  });
+  testThread.join();
+}
+
+TEST(GeckoProfiler, ThreadRegistrationInfo)
+{
+  profiler_init_main_thread_id();
+
+  TimeStamp ts = TimeStamp::Now();
+  {
+    profiler::ThreadRegistrationInfo trInfo{
+        "name", ProfilerThreadId::FromNumber(123), false, ts};
+    EXPECT_STREQ(trInfo.Name(), "name");
+    EXPECT_NE(trInfo.Name(), "name")
+        << "ThreadRegistrationInfo should keep its own copy of the name";
+    EXPECT_EQ(trInfo.RegisterTime(), ts);
+    EXPECT_EQ(trInfo.ThreadId(), ProfilerThreadId::FromNumber(123));
+    EXPECT_EQ(trInfo.IsMainThread(), false);
+  }
+
+  // Make sure the next timestamp will be different from `ts`.
+  while (TimeStamp::Now() == ts) {
+  }
+
+  {
+    profiler::ThreadRegistrationInfo trInfoHere{"Here"};
+    EXPECT_STREQ(trInfoHere.Name(), "Here");
+    EXPECT_NE(trInfoHere.Name(), "Here")
+        << "ThreadRegistrationInfo should keep its own copy of the name";
+    TimeStamp baseRegistrationTime =
+        baseprofiler::detail::GetThreadRegistrationTime();
+    if (baseRegistrationTime) {
+      EXPECT_EQ(trInfoHere.RegisterTime(), baseRegistrationTime);
+    } else {
+      EXPECT_GT(trInfoHere.RegisterTime(), ts);
+    }
+    EXPECT_EQ(trInfoHere.ThreadId(), profiler_current_thread_id());
+    EXPECT_EQ(trInfoHere.ThreadId(), profiler_main_thread_id())
+        << "Gtests are assumed to run on the main thread";
+    EXPECT_EQ(trInfoHere.IsMainThread(), true)
+        << "Gtests are assumed to run on the main thread";
+  }
+
+  {
+    // Sub-thread test.
+    // These will receive sub-thread data (to test move at thread end).
+    TimeStamp tsThread;
+    ProfilerThreadId threadThreadId;
+    UniquePtr<profiler::ThreadRegistrationInfo> trInfoThreadPtr;
+
+    std::thread testThread([&]() {
+      profiler::ThreadRegistrationInfo trInfoThread{"Thread"};
+      EXPECT_STREQ(trInfoThread.Name(), "Thread");
+      EXPECT_NE(trInfoThread.Name(), "Thread")
+          << "ThreadRegistrationInfo should keep its own copy of the name";
+      EXPECT_GT(trInfoThread.RegisterTime(), ts);
+      EXPECT_EQ(trInfoThread.ThreadId(), profiler_current_thread_id());
+      EXPECT_NE(trInfoThread.ThreadId(), profiler_main_thread_id());
+      EXPECT_EQ(trInfoThread.IsMainThread(), false);
+
+      tsThread = trInfoThread.RegisterTime();
+      threadThreadId = trInfoThread.ThreadId();
+      trInfoThreadPtr =
+          MakeUnique<profiler::ThreadRegistrationInfo>(std::move(trInfoThread));
+    });
+    testThread.join();
+
+    ASSERT_NE(trInfoThreadPtr, nullptr);
+    EXPECT_STREQ(trInfoThreadPtr->Name(), "Thread");
+    EXPECT_EQ(trInfoThreadPtr->RegisterTime(), tsThread);
+    EXPECT_EQ(trInfoThreadPtr->ThreadId(), threadThreadId);
+    EXPECT_EQ(trInfoThreadPtr->IsMainThread(), false)
+        << "Gtests are assumed to run on the main thread";
+  }
+}
+
+static constexpr ThreadProfilingFeatures scEachAndAnyThreadProfilingFeatures[] =
+    {ThreadProfilingFeatures::CPUUtilization, ThreadProfilingFeatures::Sampling,
+     ThreadProfilingFeatures::Markers, ThreadProfilingFeatures::Any};
+
+TEST(GeckoProfiler, ThreadProfilingFeaturesType)
+{
+  ASSERT_EQ(static_cast<uint32_t>(ThreadProfilingFeatures::Any), 1u + 2u + 4u)
+      << "This test assumes that there are 3 binary choices 1+2+4; "
+         "Is this test up to date?";
+
+  EXPECT_EQ(Combine(ThreadProfilingFeatures::CPUUtilization,
+                    ThreadProfilingFeatures::Sampling,
+                    ThreadProfilingFeatures::Markers),
+            ThreadProfilingFeatures::Any);
+
+  constexpr ThreadProfilingFeatures allThreadProfilingFeatures[] = {
+      ThreadProfilingFeatures::NotProfiled,
+      ThreadProfilingFeatures::CPUUtilization,
+      ThreadProfilingFeatures::Sampling, ThreadProfilingFeatures::Markers,
+      ThreadProfilingFeatures::Any};
+
+  for (ThreadProfilingFeatures f1 : allThreadProfilingFeatures) {
+    // Combine and Intersect are commutative.
+    for (ThreadProfilingFeatures f2 : allThreadProfilingFeatures) {
+      EXPECT_EQ(Combine(f1, f2), Combine(f2, f1));
+      EXPECT_EQ(Intersect(f1, f2), Intersect(f2, f1));
+    }
+
+    // Combine works like OR.
+    EXPECT_EQ(Combine(f1, f1), f1);
+    EXPECT_EQ(Combine(f1, f1, f1), f1);
+
+    // 'OR NotProfiled' doesn't change anything.
+    EXPECT_EQ(Combine(f1, ThreadProfilingFeatures::NotProfiled), f1);
+
+    // 'OR Any' makes Any.
+    EXPECT_EQ(Combine(f1, ThreadProfilingFeatures::Any),
+              ThreadProfilingFeatures::Any);
+
+    // Intersect works like AND.
+    EXPECT_EQ(Intersect(f1, f1), f1);
+    EXPECT_EQ(Intersect(f1, f1, f1), f1);
+
+    // 'AND NotProfiled' erases anything.
+    EXPECT_EQ(Intersect(f1, ThreadProfilingFeatures::NotProfiled),
+              ThreadProfilingFeatures::NotProfiled);
+
+    // 'AND Any' doesn't change anything.
+    EXPECT_EQ(Intersect(f1, ThreadProfilingFeatures::Any), f1);
+  }
+
+  for (ThreadProfilingFeatures f1 : scEachAndAnyThreadProfilingFeatures) {
+    EXPECT_TRUE(DoFeaturesIntersect(f1, f1));
+
+    // NotProfiled doesn't intersect with any feature.
+    EXPECT_FALSE(DoFeaturesIntersect(f1, ThreadProfilingFeatures::NotProfiled));
+
+    // Any intersects with any feature.
+    EXPECT_TRUE(DoFeaturesIntersect(f1, ThreadProfilingFeatures::Any));
+  }
+}
+
+static void TestConstUnlockedConstReader(
+    const profiler::ThreadRegistration::UnlockedConstReader& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  EXPECT_STREQ(aData.Info().Name(), "Test thread");
+  EXPECT_GE(aData.Info().RegisterTime(), aBeforeRegistration);
+  EXPECT_LE(aData.Info().RegisterTime(), aAfterRegistration);
+  EXPECT_EQ(aData.Info().ThreadId(), aThreadId);
+  EXPECT_FALSE(aData.Info().IsMainThread());
+
+#if (defined(_MSC_VER) || defined(__MINGW32__)) && defined(MOZ_GECKO_PROFILER)
+  HANDLE threadHandle = aData.PlatformDataCRef().ProfiledThread();
+  EXPECT_NE(threadHandle, nullptr);
+  EXPECT_EQ(ProfilerThreadId::FromNumber(::GetThreadId(threadHandle)),
+            aThreadId);
+  // Test calling QueryThreadCycleTime, we cannot assume that it will always
+  // work, but at least it shouldn't crash.
+  ULONG64 cycles;
+  (void)QueryThreadCycleTime(threadHandle, &cycles);
+#elif defined(__APPLE__) && defined(MOZ_GECKO_PROFILER)
+  // Test calling thread_info, we cannot assume that it will always work, but at
+  // least it shouldn't crash.
+  thread_basic_info_data_t threadBasicInfo;
+  mach_msg_type_number_t basicCount = THREAD_BASIC_INFO_COUNT;
+  (void)thread_info(
+      aData.PlatformDataCRef().ProfiledThread(), THREAD_BASIC_INFO,
+      reinterpret_cast<thread_info_t>(&threadBasicInfo), &basicCount);
+#elif (defined(__linux__) || defined(__ANDROID__) || defined(__FreeBSD__)) && \
+    defined(MOZ_GECKO_PROFILER)
+  // Test calling GetClockId, we cannot assume that it will always work, but at
+  // least it shouldn't crash.
+  Maybe<clockid_t> maybeClockId = aData.PlatformDataCRef().GetClockId();
+  if (maybeClockId) {
+    // Test calling clock_gettime, we cannot assume that it will always work,
+    // but at least it shouldn't crash.
+    timespec ts;
+    (void)clock_gettime(*maybeClockId, &ts);
+  }
+#else
+  (void)aData.PlatformDataCRef();
+#endif
+
+  EXPECT_GE(aData.StackTop(), aOnStackObject)
+      << "StackTop should be at &onStackChar, or higher on some "
+         "platforms";
+};
+
+static void TestConstUnlockedConstReaderAndAtomicRW(
+    const profiler::ThreadRegistration::UnlockedConstReaderAndAtomicRW& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedConstReader(aData, aBeforeRegistration, aAfterRegistration,
+                               aOnStackObject, aThreadId);
+
+  (void)aData.ProfilingStackCRef();
+
+  EXPECT_EQ(aData.ProfilingFeatures(), ThreadProfilingFeatures::NotProfiled);
+
+  EXPECT_FALSE(aData.IsSleeping());
+};
+
+static void TestUnlockedConstReaderAndAtomicRW(
+    profiler::ThreadRegistration::UnlockedConstReaderAndAtomicRW& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedConstReaderAndAtomicRW(aData, aBeforeRegistration,
+                                          aAfterRegistration, aOnStackObject,
+                                          aThreadId);
+
+  (void)aData.ProfilingStackRef();
+
+  EXPECT_FALSE(aData.IsSleeping());
+  aData.SetSleeping();
+  EXPECT_TRUE(aData.IsSleeping());
+  aData.SetAwake();
+  EXPECT_FALSE(aData.IsSleeping());
+
+  aData.ReinitializeOnResume();
+
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+  aData.SetSleeping();
+  // After sleeping, the 2nd+ calls can duplicate.
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_TRUE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_TRUE(aData.CanDuplicateLastSampleDueToSleep());
+  aData.ReinitializeOnResume();
+  // After reinit (and sleeping), the 2nd+ calls can duplicate.
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_TRUE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_TRUE(aData.CanDuplicateLastSampleDueToSleep());
+  aData.SetAwake();
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+  EXPECT_FALSE(aData.CanDuplicateLastSampleDueToSleep());
+};
+
+static void TestConstUnlockedRWForLockedProfiler(
+    const profiler::ThreadRegistration::UnlockedRWForLockedProfiler& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedConstReaderAndAtomicRW(aData, aBeforeRegistration,
+                                          aAfterRegistration, aOnStackObject,
+                                          aThreadId);
+
+  // We can't create a PSAutoLock here, so just verify that the call would
+  // compile and return the expected type.
+  static_assert(std::is_same_v<decltype(aData.GetProfiledThreadData(
+                                   std::declval<PSAutoLock>())),
+                               const ProfiledThreadData*>);
+};
+
+static void TestConstUnlockedReaderAndAtomicRWOnThread(
+    const profiler::ThreadRegistration::UnlockedReaderAndAtomicRWOnThread&
+        aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedRWForLockedProfiler(aData, aBeforeRegistration,
+                                       aAfterRegistration, aOnStackObject,
+                                       aThreadId);
+
+  EXPECT_EQ(aData.GetJSContext(), nullptr);
+};
+
+static void TestUnlockedRWForLockedProfiler(
+    profiler::ThreadRegistration::UnlockedRWForLockedProfiler& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedRWForLockedProfiler(aData, aBeforeRegistration,
+                                       aAfterRegistration, aOnStackObject,
+                                       aThreadId);
+  TestUnlockedConstReaderAndAtomicRW(aData, aBeforeRegistration,
+                                     aAfterRegistration, aOnStackObject,
+                                     aThreadId);
+
+  // No functions to test here.
+};
+
+static void TestUnlockedReaderAndAtomicRWOnThread(
+    profiler::ThreadRegistration::UnlockedReaderAndAtomicRWOnThread& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedReaderAndAtomicRWOnThread(aData, aBeforeRegistration,
+                                             aAfterRegistration, aOnStackObject,
+                                             aThreadId);
+  TestUnlockedRWForLockedProfiler(aData, aBeforeRegistration,
+                                  aAfterRegistration, aOnStackObject,
+                                  aThreadId);
+
+  // No functions to test here.
+};
+
+static void TestConstLockedRWFromAnyThread(
+    const profiler::ThreadRegistration::LockedRWFromAnyThread& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstUnlockedReaderAndAtomicRWOnThread(aData, aBeforeRegistration,
+                                             aAfterRegistration, aOnStackObject,
+                                             aThreadId);
+
+  EXPECT_EQ(aData.GetJsFrameBuffer(), nullptr);
+  EXPECT_EQ(aData.GetEventTarget(), nullptr);
+};
+
+static void TestLockedRWFromAnyThread(
+    profiler::ThreadRegistration::LockedRWFromAnyThread& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstLockedRWFromAnyThread(aData, aBeforeRegistration, aAfterRegistration,
+                                 aOnStackObject, aThreadId);
+  TestUnlockedReaderAndAtomicRWOnThread(aData, aBeforeRegistration,
+                                        aAfterRegistration, aOnStackObject,
+                                        aThreadId);
+
+  // We can't create a ProfiledThreadData nor PSAutoLock here, so just verify
+  // that the call would compile and return the expected type.
+  static_assert(std::is_same_v<decltype(aData.SetProfilingFeaturesAndData(
+                                   std::declval<ThreadProfilingFeatures>(),
+                                   std::declval<ProfiledThreadData*>(),
+                                   std::declval<PSAutoLock>())),
+                               void>);
+
+  aData.ResetMainThread(nullptr);
+
+  TimeDuration delay = TimeDuration::FromSeconds(1);
+  TimeDuration running = TimeDuration::FromSeconds(1);
+  aData.GetRunningEventDelay(TimeStamp::Now(), delay, running);
+  EXPECT_TRUE(delay.IsZero());
+  EXPECT_TRUE(running.IsZero());
+
+  aData.StartJSSampling(123u);
+  aData.StopJSSampling();
+};
+
+static void TestConstLockedRWOnThread(
+    const profiler::ThreadRegistration::LockedRWOnThread& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstLockedRWFromAnyThread(aData, aBeforeRegistration, aAfterRegistration,
+                                 aOnStackObject, aThreadId);
+
+  // No functions to test here.
+};
+
+static void TestLockedRWOnThread(
+    profiler::ThreadRegistration::LockedRWOnThread& aData,
+    const TimeStamp& aBeforeRegistration, const TimeStamp& aAfterRegistration,
+    const void* aOnStackObject,
+    ProfilerThreadId aThreadId = profiler_current_thread_id()) {
+  TestConstLockedRWOnThread(aData, aBeforeRegistration, aAfterRegistration,
+                            aOnStackObject, aThreadId);
+  TestLockedRWFromAnyThread(aData, aBeforeRegistration, aAfterRegistration,
+                            aOnStackObject, aThreadId);
+
+  // We don't want to really call SetJSContext here, so just verify that
+  // the call would compile and return the expected type.
+  static_assert(
+      std::is_same_v<decltype(aData.SetJSContext(std::declval<JSContext*>())),
+                     void>);
+  aData.ClearJSContext();
+  aData.PollJSSampling();
+};
+
+TEST(GeckoProfiler, ThreadRegistration_DataAccess)
+{
+  using TR = profiler::ThreadRegistration;
+
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  // Note that the main thread could already be registered, so we work in a new
+  // thread to test an actual registration that we control.
+
+  std::thread testThread([&]() {
+    ASSERT_FALSE(TR::IsRegistered())
+    << "A new std::thread should not start registered";
+    EXPECT_FALSE(TR::GetOnThreadPtr());
+    EXPECT_FALSE(TR::WithOnThreadRefOr([&](auto) { return true; }, false));
+
+    char onStackChar;
+
+    TimeStamp beforeRegistration = TimeStamp::Now();
+    TR tr{"Test thread", &onStackChar};
+    TimeStamp afterRegistration = TimeStamp::Now();
+
+    ASSERT_TRUE(TR::IsRegistered());
+
+    // Note: This test will mostly be about checking the correct access to
+    // thread data, depending on how it's obtained. Not all the functionality
+    // related to that data is tested (e.g., because it involves JS or other
+    // external dependencies that would be difficult to control here.)
+
+    auto TestOnThreadRef = [&](TR::OnThreadRef aOnThreadRef) {
+      // To test const-qualified member functions.
+      const TR::OnThreadRef& onThreadCRef = aOnThreadRef;
+
+      // const UnlockedConstReader (always const)
+
+      TestConstUnlockedConstReader(onThreadCRef.UnlockedConstReaderCRef(),
+                                   beforeRegistration, afterRegistration,
+                                   &onStackChar);
+      onThreadCRef.WithUnlockedConstReader(
+          [&](const TR::UnlockedConstReader& aData) {
+            TestConstUnlockedConstReader(aData, beforeRegistration,
+                                         afterRegistration, &onStackChar);
+          });
+
+      // const UnlockedConstReaderAndAtomicRW
+
+      TestConstUnlockedConstReaderAndAtomicRW(
+          onThreadCRef.UnlockedConstReaderAndAtomicRWCRef(), beforeRegistration,
+          afterRegistration, &onStackChar);
+      onThreadCRef.WithUnlockedConstReaderAndAtomicRW(
+          [&](const TR::UnlockedConstReaderAndAtomicRW& aData) {
+            TestConstUnlockedConstReaderAndAtomicRW(
+                aData, beforeRegistration, afterRegistration, &onStackChar);
+          });
+
+      // non-const UnlockedConstReaderAndAtomicRW
+
+      TestUnlockedConstReaderAndAtomicRW(
+          aOnThreadRef.UnlockedConstReaderAndAtomicRWRef(), beforeRegistration,
+          afterRegistration, &onStackChar);
+      aOnThreadRef.WithUnlockedConstReaderAndAtomicRW(
+          [&](TR::UnlockedConstReaderAndAtomicRW& aData) {
+            TestUnlockedConstReaderAndAtomicRW(aData, beforeRegistration,
+                                               afterRegistration, &onStackChar);
+          });
+
+      // const UnlockedRWForLockedProfiler
+
+      TestConstUnlockedRWForLockedProfiler(
+          onThreadCRef.UnlockedRWForLockedProfilerCRef(), beforeRegistration,
+          afterRegistration, &onStackChar);
+      onThreadCRef.WithUnlockedRWForLockedProfiler(
+          [&](const TR::UnlockedRWForLockedProfiler& aData) {
+            TestConstUnlockedRWForLockedProfiler(
+                aData, beforeRegistration, afterRegistration, &onStackChar);
+          });
+
+      // non-const UnlockedRWForLockedProfiler
+
+      TestUnlockedRWForLockedProfiler(
+          aOnThreadRef.UnlockedRWForLockedProfilerRef(), beforeRegistration,
+          afterRegistration, &onStackChar);
+      aOnThreadRef.WithUnlockedRWForLockedProfiler(
+          [&](TR::UnlockedRWForLockedProfiler& aData) {
+            TestUnlockedRWForLockedProfiler(aData, beforeRegistration,
+                                            afterRegistration, &onStackChar);
+          });
+
+      // const UnlockedReaderAndAtomicRWOnThread
+
+      TestConstUnlockedReaderAndAtomicRWOnThread(
+          onThreadCRef.UnlockedReaderAndAtomicRWOnThreadCRef(),
+          beforeRegistration, afterRegistration, &onStackChar);
+      onThreadCRef.WithUnlockedReaderAndAtomicRWOnThread(
+          [&](const TR::UnlockedReaderAndAtomicRWOnThread& aData) {
+            TestConstUnlockedReaderAndAtomicRWOnThread(
+                aData, beforeRegistration, afterRegistration, &onStackChar);
+          });
+
+      // non-const UnlockedReaderAndAtomicRWOnThread
+
+      TestUnlockedReaderAndAtomicRWOnThread(
+          aOnThreadRef.UnlockedReaderAndAtomicRWOnThreadRef(),
+          beforeRegistration, afterRegistration, &onStackChar);
+      aOnThreadRef.WithUnlockedReaderAndAtomicRWOnThread(
+          [&](TR::UnlockedReaderAndAtomicRWOnThread& aData) {
+            TestUnlockedReaderAndAtomicRWOnThread(
+                aData, beforeRegistration, afterRegistration, &onStackChar);
+          });
+
+      // LockedRWFromAnyThread
+      // Note: It cannot directly be accessed on the thread, this will be
+      // tested through LockedRWOnThread.
+
+      // const LockedRWOnThread
+
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+      {
+        TR::OnThreadRef::ConstRWOnThreadWithLock constRWOnThreadWithLock =
+            onThreadCRef.ConstLockedRWOnThread();
+        EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+        TestConstLockedRWOnThread(constRWOnThreadWithLock.DataCRef(),
+                                  beforeRegistration, afterRegistration,
+                                  &onStackChar);
+      }
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+      onThreadCRef.WithConstLockedRWOnThread(
+          [&](const TR::LockedRWOnThread& aData) {
+            EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+            TestConstLockedRWOnThread(aData, beforeRegistration,
+                                      afterRegistration, &onStackChar);
+          });
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+
+      // non-const LockedRWOnThread
+
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+      {
+        TR::OnThreadRef::RWOnThreadWithLock rwOnThreadWithLock =
+            aOnThreadRef.LockedRWOnThread();
+        EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+        TestConstLockedRWOnThread(rwOnThreadWithLock.DataCRef(),
+                                  beforeRegistration, afterRegistration,
+                                  &onStackChar);
+        TestLockedRWOnThread(rwOnThreadWithLock.DataRef(), beforeRegistration,
+                             afterRegistration, &onStackChar);
+      }
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+      aOnThreadRef.WithLockedRWOnThread([&](TR::LockedRWOnThread& aData) {
+        EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+        TestLockedRWOnThread(aData, beforeRegistration, afterRegistration,
+                             &onStackChar);
+      });
+      EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+    };
+
+    TR::OnThreadPtr onThreadPtr = TR::GetOnThreadPtr();
+    ASSERT_TRUE(onThreadPtr);
+    TestOnThreadRef(*onThreadPtr);
+
+    TR::WithOnThreadRef(
+        [&](TR::OnThreadRef aOnThreadRef) { TestOnThreadRef(aOnThreadRef); });
+
+    EXPECT_TRUE(TR::WithOnThreadRefOr(
+        [&](TR::OnThreadRef aOnThreadRef) {
+          TestOnThreadRef(aOnThreadRef);
+          return true;
+        },
+        false));
+  });
+  testThread.join();
+}
+
+// Thread name if registered, nullptr otherwise.
+static const char* GetThreadName() {
+  return profiler::ThreadRegistration::WithOnThreadRefOr(
+      [](profiler::ThreadRegistration::OnThreadRef onThreadRef) {
+        return onThreadRef.WithUnlockedConstReader(
+            [](const profiler::ThreadRegistration::UnlockedConstReader& aData) {
+              return aData.Info().Name();
+            });
+      },
+      nullptr);
+}
+
+// Get the thread name, as registered in the PRThread, nullptr on failure.
+static const char* GetPRThreadName() {
+  nsIThread* nsThread = NS_GetCurrentThread();
+  if (!nsThread) {
+    return nullptr;
+  }
+  PRThread* prThread = nullptr;
+  if (NS_FAILED(nsThread->GetPRThread(&prThread))) {
+    return nullptr;
+  }
+  if (!prThread) {
+    return nullptr;
+  }
+  return PR_GetThreadName(prThread);
+}
+
+TEST(GeckoProfiler, ThreadRegistration_MainThreadName)
+{
+  EXPECT_TRUE(profiler::ThreadRegistration::IsRegistered());
+  EXPECT_STREQ(GetThreadName(), "GeckoMain");
+
+  // Check that the real thread name (outside the profiler) is *not* GeckoMain.
+  EXPECT_STRNE(GetPRThreadName(), "GeckoMain");
+}
+
+TEST(GeckoProfiler, ThreadRegistration_NestedRegistrations)
+{
+  using TR = profiler::ThreadRegistration;
+
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  // Note that the main thread could already be registered, so we work in a new
+  // thread to test actual registrations that we control.
+
+  std::thread testThread([&]() {
+    ASSERT_FALSE(TR::IsRegistered())
+    << "A new std::thread should not start registered";
+
+    char onStackChar;
+
+    // Blocks {} are mostly for clarity, but some control on-stack registration
+    // lifetimes.
+
+    // On-stack registration.
+    {
+      TR rt{"Test thread #1", &onStackChar};
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #1");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #1");
+    }
+    ASSERT_FALSE(TR::IsRegistered());
+
+    // Off-stack registration.
+    {
+      TR::RegisterThread("Test thread #2", &onStackChar);
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #2");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #2");
+
+      TR::UnregisterThread();
+      ASSERT_FALSE(TR::IsRegistered());
+    }
+
+    // Extra un-registration should be ignored.
+    TR::UnregisterThread();
+    ASSERT_FALSE(TR::IsRegistered());
+
+    // Nested on-stack.
+    {
+      TR rt2{"Test thread #3", &onStackChar};
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #3");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #3");
+
+      {
+        TR rt3{"Test thread #4", &onStackChar};
+        ASSERT_TRUE(TR::IsRegistered());
+        EXPECT_STREQ(GetThreadName(), "Test thread #3")
+            << "Nested registration shouldn't change the name";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #3")
+            << "Nested registration shouldn't change the PRThread name";
+      }
+      ASSERT_TRUE(TR::IsRegistered())
+      << "Thread should still be registered after nested un-registration";
+      EXPECT_STREQ(GetThreadName(), "Test thread #3")
+          << "Thread should still be registered after nested un-registration";
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #3");
+    }
+    ASSERT_FALSE(TR::IsRegistered());
+
+    // Nested off-stack.
+    {
+      TR::RegisterThread("Test thread #5", &onStackChar);
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #5");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #5");
+
+      {
+        TR::RegisterThread("Test thread #6", &onStackChar);
+        ASSERT_TRUE(TR::IsRegistered());
+        EXPECT_STREQ(GetThreadName(), "Test thread #5")
+            << "Nested registration shouldn't change the name";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #5")
+            << "Nested registration shouldn't change the PRThread name";
+
+        TR::UnregisterThread();
+        ASSERT_TRUE(TR::IsRegistered())
+        << "Thread should still be registered after nested un-registration";
+        EXPECT_STREQ(GetThreadName(), "Test thread #5")
+            << "Thread should still be registered after nested un-registration";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #5");
+      }
+
+      TR::UnregisterThread();
+      ASSERT_FALSE(TR::IsRegistered());
+    }
+
+    // Nested on- and off-stack.
+    {
+      TR rt2{"Test thread #7", &onStackChar};
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #7");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #7");
+
+      {
+        TR::RegisterThread("Test thread #8", &onStackChar);
+        ASSERT_TRUE(TR::IsRegistered());
+        EXPECT_STREQ(GetThreadName(), "Test thread #7")
+            << "Nested registration shouldn't change the name";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #7")
+            << "Nested registration shouldn't change the PRThread name";
+
+        TR::UnregisterThread();
+        ASSERT_TRUE(TR::IsRegistered())
+        << "Thread should still be registered after nested un-registration";
+        EXPECT_STREQ(GetThreadName(), "Test thread #7")
+            << "Thread should still be registered after nested un-registration";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #7");
+      }
+    }
+    ASSERT_FALSE(TR::IsRegistered());
+
+    // Nested off- and on-stack.
+    {
+      TR::RegisterThread("Test thread #9", &onStackChar);
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #9");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #9");
+
+      {
+        TR rt3{"Test thread #10", &onStackChar};
+        ASSERT_TRUE(TR::IsRegistered());
+        EXPECT_STREQ(GetThreadName(), "Test thread #9")
+            << "Nested registration shouldn't change the name";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #9")
+            << "Nested registration shouldn't change the PRThread name";
+      }
+      ASSERT_TRUE(TR::IsRegistered())
+      << "Thread should still be registered after nested un-registration";
+      EXPECT_STREQ(GetThreadName(), "Test thread #9")
+          << "Thread should still be registered after nested un-registration";
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #9");
+
+      TR::UnregisterThread();
+      ASSERT_FALSE(TR::IsRegistered());
+    }
+
+    // Excess UnregisterThread with on-stack TR.
+    {
+      TR rt2{"Test thread #11", &onStackChar};
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #11");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #11");
+
+      TR::UnregisterThread();
+      ASSERT_TRUE(TR::IsRegistered())
+      << "On-stack thread should still be registered after off-stack "
+         "un-registration";
+      EXPECT_STREQ(GetThreadName(), "Test thread #11")
+          << "On-stack thread should still be registered after off-stack "
+             "un-registration";
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #11");
+    }
+    ASSERT_FALSE(TR::IsRegistered());
+
+    // Excess on-thread TR destruction with already-unregistered root off-thread
+    // registration.
+    {
+      TR::RegisterThread("Test thread #12", &onStackChar);
+      ASSERT_TRUE(TR::IsRegistered());
+      EXPECT_STREQ(GetThreadName(), "Test thread #12");
+      EXPECT_STREQ(GetPRThreadName(), "Test thread #12");
+
+      {
+        TR rt3{"Test thread #13", &onStackChar};
+        ASSERT_TRUE(TR::IsRegistered());
+        EXPECT_STREQ(GetThreadName(), "Test thread #12")
+            << "Nested registration shouldn't change the name";
+        EXPECT_STREQ(GetPRThreadName(), "Test thread #12")
+            << "Nested registration shouldn't change the PRThread name";
+
+        // Note that we unregister the root registration, while nested `rt3` is
+        // still alive.
+        TR::UnregisterThread();
+        ASSERT_FALSE(TR::IsRegistered())
+        << "UnregisterThread() of the root RegisterThread() should always work";
+
+        // At this end of this block, `rt3` will be destroyed, but nothing
+        // should happen.
+      }
+      ASSERT_FALSE(TR::IsRegistered());
+    }
+
+    ASSERT_FALSE(TR::IsRegistered());
+  });
+  testThread.join();
+}
+
+TEST(GeckoProfiler, ThreadRegistry_DataAccess)
+{
+  using TR = profiler::ThreadRegistration;
+  using TRy = profiler::ThreadRegistry;
+
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  // Note that the main thread could already be registered, so we work in a new
+  // thread to test an actual registration that we control.
+
+  std::thread testThread([&]() {
+    ASSERT_FALSE(TR::IsRegistered())
+    << "A new std::thread should not start registered";
+    EXPECT_FALSE(TR::GetOnThreadPtr());
+    EXPECT_FALSE(TR::WithOnThreadRefOr([&](auto) { return true; }, false));
+
+    char onStackChar;
+
+    TimeStamp beforeRegistration = TimeStamp::Now();
+    TR tr{"Test thread", &onStackChar};
+    TimeStamp afterRegistration = TimeStamp::Now();
+
+    ASSERT_TRUE(TR::IsRegistered());
+
+    // Note: This test will mostly be about checking the correct access to
+    // thread data, depending on how it's obtained. Not all the functionality
+    // related to that data is tested (e.g., because it involves JS or other
+    // external dependencies that would be difficult to control here.)
+
+    const ProfilerThreadId testThreadId = profiler_current_thread_id();
+
+    auto testThroughRegistry = [&]() {
+      auto TestOffThreadRef = [&](TRy::OffThreadRef aOffThreadRef) {
+        // To test const-qualified member functions.
+        const TRy::OffThreadRef& offThreadCRef = aOffThreadRef;
+
+        // const UnlockedConstReader (always const)
+
+        TestConstUnlockedConstReader(offThreadCRef.UnlockedConstReaderCRef(),
+                                     beforeRegistration, afterRegistration,
+                                     &onStackChar, testThreadId);
+        offThreadCRef.WithUnlockedConstReader(
+            [&](const TR::UnlockedConstReader& aData) {
+              TestConstUnlockedConstReader(aData, beforeRegistration,
+                                           afterRegistration, &onStackChar,
+                                           testThreadId);
+            });
+
+        // const UnlockedConstReaderAndAtomicRW
+
+        TestConstUnlockedConstReaderAndAtomicRW(
+            offThreadCRef.UnlockedConstReaderAndAtomicRWCRef(),
+            beforeRegistration, afterRegistration, &onStackChar, testThreadId);
+        offThreadCRef.WithUnlockedConstReaderAndAtomicRW(
+            [&](const TR::UnlockedConstReaderAndAtomicRW& aData) {
+              TestConstUnlockedConstReaderAndAtomicRW(
+                  aData, beforeRegistration, afterRegistration, &onStackChar,
+                  testThreadId);
+            });
+
+        // non-const UnlockedConstReaderAndAtomicRW
+
+        TestUnlockedConstReaderAndAtomicRW(
+            aOffThreadRef.UnlockedConstReaderAndAtomicRWRef(),
+            beforeRegistration, afterRegistration, &onStackChar, testThreadId);
+        aOffThreadRef.WithUnlockedConstReaderAndAtomicRW(
+            [&](TR::UnlockedConstReaderAndAtomicRW& aData) {
+              TestUnlockedConstReaderAndAtomicRW(aData, beforeRegistration,
+                                                 afterRegistration,
+                                                 &onStackChar, testThreadId);
+            });
+
+        // const UnlockedRWForLockedProfiler
+
+        TestConstUnlockedRWForLockedProfiler(
+            offThreadCRef.UnlockedRWForLockedProfilerCRef(), beforeRegistration,
+            afterRegistration, &onStackChar, testThreadId);
+        offThreadCRef.WithUnlockedRWForLockedProfiler(
+            [&](const TR::UnlockedRWForLockedProfiler& aData) {
+              TestConstUnlockedRWForLockedProfiler(aData, beforeRegistration,
+                                                   afterRegistration,
+                                                   &onStackChar, testThreadId);
+            });
+
+        // non-const UnlockedRWForLockedProfiler
+
+        TestUnlockedRWForLockedProfiler(
+            aOffThreadRef.UnlockedRWForLockedProfilerRef(), beforeRegistration,
+            afterRegistration, &onStackChar, testThreadId);
+        aOffThreadRef.WithUnlockedRWForLockedProfiler(
+            [&](TR::UnlockedRWForLockedProfiler& aData) {
+              TestUnlockedRWForLockedProfiler(aData, beforeRegistration,
+                                              afterRegistration, &onStackChar,
+                                              testThreadId);
+            });
+
+        // UnlockedReaderAndAtomicRWOnThread
+        // Note: It cannot directly be accessed off the thread, this will be
+        // tested through LockedRWFromAnyThread.
+
+        // const LockedRWFromAnyThread
+
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+        {
+          TRy::OffThreadRef::ConstRWFromAnyThreadWithLock
+              constRWFromAnyThreadWithLock =
+                  offThreadCRef.ConstLockedRWFromAnyThread();
+          if (profiler_current_thread_id() == testThreadId) {
+            EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+          }
+          TestConstLockedRWFromAnyThread(
+              constRWFromAnyThreadWithLock.DataCRef(), beforeRegistration,
+              afterRegistration, &onStackChar, testThreadId);
+        }
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+        offThreadCRef.WithConstLockedRWFromAnyThread(
+            [&](const TR::LockedRWFromAnyThread& aData) {
+              if (profiler_current_thread_id() == testThreadId) {
+                EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+              }
+              TestConstLockedRWFromAnyThread(aData, beforeRegistration,
+                                             afterRegistration, &onStackChar,
+                                             testThreadId);
+            });
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+
+        // non-const LockedRWFromAnyThread
+
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+        {
+          TRy::OffThreadRef::RWFromAnyThreadWithLock rwFromAnyThreadWithLock =
+              aOffThreadRef.LockedRWFromAnyThread();
+          if (profiler_current_thread_id() == testThreadId) {
+            EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+          }
+          TestLockedRWFromAnyThread(rwFromAnyThreadWithLock.DataRef(),
+                                    beforeRegistration, afterRegistration,
+                                    &onStackChar, testThreadId);
+        }
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+        aOffThreadRef.WithLockedRWFromAnyThread(
+            [&](TR::LockedRWFromAnyThread& aData) {
+              if (profiler_current_thread_id() == testThreadId) {
+                EXPECT_TRUE(TR::IsDataMutexLockedOnCurrentThread());
+              }
+              TestLockedRWFromAnyThread(aData, beforeRegistration,
+                                        afterRegistration, &onStackChar,
+                                        testThreadId);
+            });
+        EXPECT_FALSE(TR::IsDataMutexLockedOnCurrentThread());
+
+        // LockedRWOnThread
+        // Note: It can never be accessed off the thread.
+      };
+
+      int ranTest = 0;
+      TRy::WithOffThreadRef(testThreadId, [&](TRy::OffThreadRef aOffThreadRef) {
+        TestOffThreadRef(aOffThreadRef);
+        ++ranTest;
+      });
+      EXPECT_EQ(ranTest, 1);
+
+      EXPECT_TRUE(TRy::WithOffThreadRefOr(
+          testThreadId,
+          [&](TRy::OffThreadRef aOffThreadRef) {
+            TestOffThreadRef(aOffThreadRef);
+            return true;
+          },
+          false));
+
+      ranTest = 0;
+      EXPECT_FALSE(TRy::IsRegistryMutexLockedOnCurrentThread());
+      for (TRy::OffThreadRef offThreadRef : TRy::LockedRegistry{}) {
+        EXPECT_TRUE(TRy::IsRegistryMutexLockedOnCurrentThread() ||
+                    !TR::IsRegistered());
+        if (offThreadRef.UnlockedConstReaderCRef().Info().ThreadId() ==
+            testThreadId) {
+          TestOffThreadRef(offThreadRef);
+          ++ranTest;
+        }
+      }
+      EXPECT_EQ(ranTest, 1);
+      EXPECT_FALSE(TRy::IsRegistryMutexLockedOnCurrentThread());
+
+      {
+        ranTest = 0;
+        EXPECT_FALSE(TRy::IsRegistryMutexLockedOnCurrentThread());
+        TRy::LockedRegistry lockedRegistry{};
+        EXPECT_TRUE(TRy::IsRegistryMutexLockedOnCurrentThread() ||
+                    !TR::IsRegistered());
+        for (TRy::OffThreadRef offThreadRef : lockedRegistry) {
+          if (offThreadRef.UnlockedConstReaderCRef().Info().ThreadId() ==
+              testThreadId) {
+            TestOffThreadRef(offThreadRef);
+            ++ranTest;
+          }
+        }
+        EXPECT_EQ(ranTest, 1);
+      }
+      EXPECT_FALSE(TRy::IsRegistryMutexLockedOnCurrentThread());
+    };
+
+    // Test on the current thread.
+    testThroughRegistry();
+
+    // Test from another thread.
+    std::thread otherThread([&]() {
+      ASSERT_NE(profiler_current_thread_id(), testThreadId);
+      testThroughRegistry();
+
+      // Test that this unregistered thread is really not registered.
+      int ranTest = 0;
+      TRy::WithOffThreadRef(
+          profiler_current_thread_id(),
+          [&](TRy::OffThreadRef aOffThreadRef) { ++ranTest; });
+      EXPECT_EQ(ranTest, 0);
+
+      EXPECT_FALSE(TRy::WithOffThreadRefOr(
+          profiler_current_thread_id(),
+          [&](TRy::OffThreadRef aOffThreadRef) {
+            ++ranTest;
+            return true;
+          },
+          false));
+      EXPECT_EQ(ranTest, 0);
+    });
+    otherThread.join();
+  });
+  testThread.join();
+}
+
+TEST(GeckoProfiler, ThreadRegistration_RegistrationEdgeCases)
+{
+  using TR = profiler::ThreadRegistration;
+  using TRy = profiler::ThreadRegistry;
+
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  // Note that the main thread could already be registered, so we work in a new
+  // thread to test an actual registration that we control.
+
+  int registrationCount = 0;
+  int otherThreadLoops = 0;
+  int otherThreadReads = 0;
+
+  // This thread will register and unregister in a loop, with some pauses.
+  // Another thread will attempty to access the test thread, and lock its data.
+  // The main goal is to check edges cases around (un)registrations.
+  std::thread testThread([&]() {
+    const ProfilerThreadId testThreadId = profiler_current_thread_id();
+
+    const TimeStamp endTestAt = TimeStamp::Now() + TimeDuration::FromSeconds(1);
+
+    std::thread otherThread([&]() {
+      // Initial sleep so that testThread can start its loop.
+      PR_Sleep(PR_MillisecondsToInterval(1));
+
+      while (TimeStamp::Now() < endTestAt) {
+        ++otherThreadLoops;
+
+        TRy::WithOffThreadRef(testThreadId, [&](TRy::OffThreadRef
+                                                    aOffThreadRef) {
+          if (otherThreadLoops % 1000 == 0) {
+            PR_Sleep(PR_MillisecondsToInterval(1));
+          }
+          TRy::OffThreadRef::RWFromAnyThreadWithLock rwFromAnyThreadWithLock =
+              aOffThreadRef.LockedRWFromAnyThread();
+          ++otherThreadReads;
+          if (otherThreadReads % 1000 == 0) {
+            PR_Sleep(PR_MillisecondsToInterval(1));
+          }
+        });
+      }
+    });
+
+    while (TimeStamp::Now() < endTestAt) {
+      ASSERT_FALSE(TR::IsRegistered())
+      << "A new std::thread should not start registered";
+      EXPECT_FALSE(TR::GetOnThreadPtr());
+      EXPECT_FALSE(TR::WithOnThreadRefOr([&](auto) { return true; }, false));
+
+      char onStackChar;
+
+      TR tr{"Test thread", &onStackChar};
+      ++registrationCount;
+
+      ASSERT_TRUE(TR::IsRegistered());
+
+      int ranTest = 0;
+      TRy::WithOffThreadRef(testThreadId, [&](TRy::OffThreadRef aOffThreadRef) {
+        if (registrationCount % 2000 == 0) {
+          PR_Sleep(PR_MillisecondsToInterval(1));
+        }
+        ++ranTest;
+      });
+      EXPECT_EQ(ranTest, 1);
+
+      if (registrationCount % 1000 == 0) {
+        PR_Sleep(PR_MillisecondsToInterval(1));
+      }
+    }
+
+    otherThread.join();
+  });
+
+  testThread.join();
+
+  // It's difficult to guess what these numbers should be, but they definitely
+  // should be non-zero. The main goal was to test that nothing goes wrong.
+  EXPECT_GT(registrationCount, 0);
+  EXPECT_GT(otherThreadLoops, 0);
+  EXPECT_GT(otherThreadReads, 0);
+}
+
+#ifdef MOZ_GECKO_PROFILER
+
+TEST(BaseProfiler, BlocksRingBuffer)
+{
+  constexpr uint32_t MBSize = 256;
+  uint8_t buffer[MBSize * 3];
+  for (size_t i = 0; i < MBSize * 3; ++i) {
+    buffer[i] = uint8_t('A' + i);
+  }
+  BlocksRingBuffer rb(BlocksRingBuffer::ThreadSafety::WithMutex,
+                      &buffer[MBSize], MakePowerOfTwo32<MBSize>());
+
+  {
+    nsCString cs("nsCString"_ns);
+    nsString s(u"nsString"_ns);
+    nsAutoCString acs("nsAutoCString"_ns);
+    nsAutoString as(u"nsAutoString"_ns);
+    nsAutoCStringN<8> acs8("nsAutoCStringN"_ns);
+    nsAutoStringN<8> as8(u"nsAutoStringN"_ns);
+    JS::UniqueChars jsuc = JS_smprintf("%s", "JS::UniqueChars");
+
+    rb.PutObjects(cs, s, acs, as, acs8, as8, jsuc);
+  }
+
+  rb.ReadEach([](ProfileBufferEntryReader& aER) {
+    ASSERT_EQ(aER.ReadObject<nsCString>(), "nsCString"_ns);
+    ASSERT_EQ(aER.ReadObject<nsString>(), u"nsString"_ns);
+    ASSERT_EQ(aER.ReadObject<nsAutoCString>(), "nsAutoCString"_ns);
+    ASSERT_EQ(aER.ReadObject<nsAutoString>(), u"nsAutoString"_ns);
+    ASSERT_EQ(aER.ReadObject<nsAutoCStringN<8>>(), "nsAutoCStringN"_ns);
+    ASSERT_EQ(aER.ReadObject<nsAutoStringN<8>>(), u"nsAutoStringN"_ns);
+    auto jsuc2 = aER.ReadObject<JS::UniqueChars>();
+    ASSERT_TRUE(!!jsuc2);
+    ASSERT_TRUE(strcmp(jsuc2.get(), "JS::UniqueChars") == 0);
+  });
+
+  // Everything around the sub-buffer should be unchanged.
+  for (size_t i = 0; i < MBSize; ++i) {
+    ASSERT_EQ(buffer[i], uint8_t('A' + i));
+  }
+  for (size_t i = MBSize * 2; i < MBSize * 3; ++i) {
+    ASSERT_EQ(buffer[i], uint8_t('A' + i));
+  }
+}
+
+// Common JSON checks.
+
+// Check that the given JSON string include no JSON whitespace characters
+// (excluding those in property names and strings).
+void JSONWhitespaceCheck(const char* aOutput) {
+  ASSERT_NE(aOutput, nullptr);
+
+  enum class State { Data, String, StringEscaped };
+  State state = State::Data;
+  size_t length = 0;
+  size_t whitespaces = 0;
+  for (const char* p = aOutput; *p != '\0'; ++p) {
+    ++length;
+    const char c = *p;
+
+    switch (state) {
+      case State::Data:
+        if (c == '\n' || c == '\r' || c == ' ' || c == '\t') {
+          ++whitespaces;
+        } else if (c == '"') {
+          state = State::String;
+        }
+        break;
+
+      case State::String:
+        if (c == '"') {
+          state = State::Data;
+        } else if (c == '\\') {
+          state = State::StringEscaped;
+        }
+        break;
+
+      case State::StringEscaped:
+        state = State::String;
+        break;
+    }
+  }
+
+  EXPECT_EQ(whitespaces, 0u);
+  EXPECT_GT(length, 0u);
+}
+
+// Does the GETTER return a non-null TYPE? (Non-critical)
+#  define EXPECT_HAS_JSON(GETTER, TYPE)              \
+    do {                                             \
+      if ((GETTER).isNull()) {                       \
+        EXPECT_FALSE((GETTER).isNull())              \
+            << #GETTER " doesn't exist or is null";  \
+      } else if (!(GETTER).is##TYPE()) {             \
+        EXPECT_TRUE((GETTER).is##TYPE())             \
+            << #GETTER " didn't return type " #TYPE; \
+      }                                              \
+    } while (false)
+
+// Does the GETTER return a non-null TYPE? (Critical)
+#  define ASSERT_HAS_JSON(GETTER, TYPE) \
+    do {                                \
+      ASSERT_FALSE((GETTER).isNull());  \
+      ASSERT_TRUE((GETTER).is##TYPE()); \
+    } while (false)
+
+// Does the GETTER return a non-null TYPE? (Critical)
+// If yes, store the reference to Json::Value into VARIABLE.
+#  define GET_JSON(VARIABLE, GETTER, TYPE) \
+    ASSERT_HAS_JSON(GETTER, TYPE);         \
+    const Json::Value& VARIABLE = (GETTER)
+
+// Does the GETTER return a non-null TYPE? (Critical)
+// If yes, store the value as `const TYPE` into VARIABLE.
+#  define GET_JSON_VALUE(VARIABLE, GETTER, TYPE) \
+    ASSERT_HAS_JSON(GETTER, TYPE);               \
+    const auto VARIABLE = (GETTER).as##TYPE()
+
+// Non-const GET_JSON_VALUE.
+#  define GET_JSON_MUTABLE_VALUE(VARIABLE, GETTER, TYPE) \
+    ASSERT_HAS_JSON(GETTER, TYPE);                       \
+    auto VARIABLE = (GETTER).as##TYPE()
+
+// Checks that the GETTER's value is present, is of the expected TYPE, and has
+// the expected VALUE. (Non-critical)
+#  define EXPECT_EQ_JSON(GETTER, TYPE, VALUE)        \
+    do {                                             \
+      if ((GETTER).isNull()) {                       \
+        EXPECT_FALSE((GETTER).isNull())              \
+            << #GETTER " doesn't exist or is null";  \
+      } else if (!(GETTER).is##TYPE()) {             \
+        EXPECT_TRUE((GETTER).is##TYPE())             \
+            << #GETTER " didn't return type " #TYPE; \
+      } else {                                       \
+        EXPECT_EQ((GETTER).as##TYPE(), (VALUE));     \
+      }                                              \
+    } while (false)
+
+// Checks that the GETTER's value is present, and is a valid index into the
+// STRINGTABLE array, pointing at the expected STRING.
+#  define EXPECT_EQ_STRINGTABLE(GETTER, STRINGTABLE, STRING)                 \
+    do {                                                                     \
+      if ((GETTER).isNull()) {                                               \
+        EXPECT_FALSE((GETTER).isNull())                                      \
+            << #GETTER " doesn't exist or is null";                          \
+      } else if (!(GETTER).isUInt()) {                                       \
+        EXPECT_TRUE((GETTER).isUInt()) << #GETTER " didn't return an index"; \
+      } else {                                                               \
+        EXPECT_LT((GETTER).asUInt(), (STRINGTABLE).size());                  \
+        EXPECT_EQ_JSON((STRINGTABLE)[(GETTER).asUInt()], String, (STRING));  \
+      }                                                                      \
+    } while (false)
+
+#  define EXPECT_JSON_ARRAY_CONTAINS(GETTER, TYPE, VALUE)                     \
+    do {                                                                      \
+      if ((GETTER).isNull()) {                                                \
+        EXPECT_FALSE((GETTER).isNull())                                       \
+            << #GETTER " doesn't exist or is null";                           \
+      } else if (!(GETTER).isArray()) {                                       \
+        EXPECT_TRUE((GETTER).is##TYPE()) << #GETTER " is not an array";       \
+      } else if (const Json::ArrayIndex size = (GETTER).size(); size == 0u) { \
+        EXPECT_NE(size, 0u) << #GETTER " is an empty array";                  \
+      } else {                                                                \
+        bool found = false;                                                   \
+        for (Json::ArrayIndex i = 0; i < size; ++i) {                         \
+          if (!(GETTER)[i].is##TYPE()) {                                      \
+            EXPECT_TRUE((GETTER)[i].is##TYPE())                               \
+                << #GETTER "[" << i << "] is not " #TYPE;                     \
+            break;                                                            \
+          }                                                                   \
+          if ((GETTER)[i].as##TYPE() == (VALUE)) {                            \
+            found = true;                                                     \
+            break;                                                            \
+          }                                                                   \
+        }                                                                     \
+        EXPECT_TRUE(found) << #GETTER " doesn't contain " #VALUE;             \
+      }                                                                       \
+    } while (false)
+
+#  define EXPECT_JSON_ARRAY_EXCLUDES(GETTER, TYPE, VALUE)               \
+    do {                                                                \
+      if ((GETTER).isNull()) {                                          \
+        EXPECT_FALSE((GETTER).isNull())                                 \
+            << #GETTER " doesn't exist or is null";                     \
+      } else if (!(GETTER).isArray()) {                                 \
+        EXPECT_TRUE((GETTER).is##TYPE()) << #GETTER " is not an array"; \
+      } else {                                                          \
+        const Json::ArrayIndex size = (GETTER).size();                  \
+        for (Json::ArrayIndex i = 0; i < size; ++i) {                   \
+          if (!(GETTER)[i].is##TYPE()) {                                \
+            EXPECT_TRUE((GETTER)[i].is##TYPE())                         \
+                << #GETTER "[" << i << "] is not " #TYPE;               \
+            break;                                                      \
+          }                                                             \
+          if ((GETTER)[i].as##TYPE() == (VALUE)) {                      \
+            EXPECT_TRUE((GETTER)[i].as##TYPE() != (VALUE))              \
+                << #GETTER " contains " #VALUE;                         \
+            break;                                                      \
+          }                                                             \
+        }                                                               \
+      }                                                                 \
+    } while (false)
+
+// Check that the given process root contains all the expected properties.
+static void JSONRootCheck(const Json::Value& aRoot,
+                          bool aWithMainThread = true) {
+  ASSERT_TRUE(aRoot.isObject());
+
+  EXPECT_HAS_JSON(aRoot["libs"], Array);
+
+  GET_JSON(meta, aRoot["meta"], Object);
+  EXPECT_HAS_JSON(meta["version"], UInt);
+  EXPECT_HAS_JSON(meta["startTime"], Double);
+  EXPECT_HAS_JSON(meta["profilingStartTime"], Double);
+  EXPECT_HAS_JSON(meta["contentEarliestTime"], Double);
+  EXPECT_HAS_JSON(meta["profilingEndTime"], Double);
+
+  EXPECT_HAS_JSON(aRoot["pages"], Array);
+
+  EXPECT_HAS_JSON(aRoot["profilerOverhead"], Object);
+
+  // "counters" is only present if there is any data to report.
+  // Test that expect "counters" should test for its presence first.
+  if (aRoot.isMember("counters")) {
+    // We have "counters", test their overall validity.
+    GET_JSON(counters, aRoot["counters"], Array);
+    for (const Json::Value& counter : counters) {
+      ASSERT_TRUE(counter.isObject());
+      EXPECT_HAS_JSON(counter["name"], String);
+      EXPECT_HAS_JSON(counter["category"], String);
+      EXPECT_HAS_JSON(counter["description"], String);
+      GET_JSON(sampleGroups, counter["sample_groups"], Array);
+      for (const Json::Value& sampleGroup : sampleGroups) {
+        ASSERT_TRUE(sampleGroup.isObject());
+        EXPECT_HAS_JSON(sampleGroup["id"], UInt);
+
+        GET_JSON(samples, sampleGroup["samples"], Object);
+        GET_JSON(samplesSchema, samples["schema"], Object);
+        EXPECT_GE(samplesSchema.size(), 3u);
+        GET_JSON_VALUE(samplesTime, samplesSchema["time"], UInt);
+        GET_JSON_VALUE(samplesNumber, samplesSchema["number"], UInt);
+        GET_JSON_VALUE(samplesCount, samplesSchema["count"], UInt);
+        GET_JSON(samplesData, samples["data"], Array);
+        double previousTime = 0.0;
+        for (const Json::Value& sample : samplesData) {
+          ASSERT_TRUE(sample.isArray());
+          GET_JSON_VALUE(time, sample[samplesTime], Double);
+          EXPECT_GE(time, previousTime);
+          previousTime = time;
+          if (sample.isValidIndex(samplesNumber)) {
+            EXPECT_HAS_JSON(sample[samplesNumber], UInt64);
+          }
+          if (sample.isValidIndex(samplesCount)) {
+            EXPECT_HAS_JSON(sample[samplesCount], Int64);
+          }
+        }
+      }
+    }
+  }
+
+  GET_JSON(threads, aRoot["threads"], Array);
+  const Json::ArrayIndex threadCount = threads.size();
+  for (Json::ArrayIndex i = 0; i < threadCount; ++i) {
+    GET_JSON(thread, threads[i], Object);
+    EXPECT_HAS_JSON(thread["processType"], String);
+    EXPECT_HAS_JSON(thread["name"], String);
+    EXPECT_HAS_JSON(thread["registerTime"], Double);
+    GET_JSON(samples, thread["samples"], Object);
+    EXPECT_HAS_JSON(thread["markers"], Object);
+    EXPECT_HAS_JSON(thread["pid"], Int64);
+    EXPECT_HAS_JSON(thread["tid"], Int64);
+    GET_JSON(stackTable, thread["stackTable"], Object);
+    GET_JSON(frameTable, thread["frameTable"], Object);
+    GET_JSON(stringTable, thread["stringTable"], Array);
+
+    GET_JSON(stackTableSchema, stackTable["schema"], Object);
+    EXPECT_GE(stackTableSchema.size(), 2u);
+    GET_JSON_VALUE(stackTablePrefix, stackTableSchema["prefix"], UInt);
+    GET_JSON_VALUE(stackTableFrame, stackTableSchema["frame"], UInt);
+    GET_JSON(stackTableData, stackTable["data"], Array);
+
+    GET_JSON(frameTableSchema, frameTable["schema"], Object);
+    EXPECT_GE(frameTableSchema.size(), 1u);
+    GET_JSON_VALUE(frameTableLocation, frameTableSchema["location"], UInt);
+    GET_JSON(frameTableData, frameTable["data"], Array);
+
+    GET_JSON(samplesSchema, samples["schema"], Object);
+    GET_JSON_VALUE(sampleStackIndex, samplesSchema["stack"], UInt);
+    GET_JSON(samplesData, samples["data"], Array);
+    for (const Json::Value& sample : samplesData) {
+      ASSERT_TRUE(sample.isArray());
+      if (sample.isValidIndex(sampleStackIndex)) {
+        if (!sample[sampleStackIndex].isNull()) {
+          GET_JSON_MUTABLE_VALUE(stack, sample[sampleStackIndex], UInt);
+          EXPECT_TRUE(stackTableData.isValidIndex(stack));
+          for (;;) {
+            // `stack` (from the sample, or from the callee frame's "prefix" in
+            // the previous loop) points into the stackTable.
+            GET_JSON(stackTableEntry, stackTableData[stack], Array);
+            GET_JSON_VALUE(frame, stackTableEntry[stackTableFrame], UInt);
+
+            // The stackTable entry's "frame" points into the frameTable.
+            EXPECT_TRUE(frameTableData.isValidIndex(frame));
+            GET_JSON(frameTableEntry, frameTableData[frame], Array);
+            GET_JSON_VALUE(location, frameTableEntry[frameTableLocation], UInt);
+
+            // The frameTable entry's "location" points at a string.
+            EXPECT_TRUE(stringTable.isValidIndex(location));
+
+            // The stackTable entry's "prefix" is null for the root frame.
+            if (stackTableEntry[stackTablePrefix].isNull()) {
+              break;
+            }
+            // Otherwise it recursively points at the caller in the stackTable.
+            GET_JSON_VALUE(prefix, stackTableEntry[stackTablePrefix], UInt);
+            EXPECT_TRUE(stackTableData.isValidIndex(prefix));
+            stack = prefix;
+          }
+        }
+      }
+    }
+  }
+
+  if (aWithMainThread) {
+    ASSERT_GT(threadCount, 0u);
+    GET_JSON(thread0, threads[0], Object);
+    EXPECT_EQ_JSON(thread0["name"], String, "GeckoMain");
+  }
+
+  EXPECT_HAS_JSON(aRoot["pausedRanges"], Array);
+
+  const Json::Value& processes = aRoot["processes"];
+  if (!processes.isNull()) {
+    ASSERT_TRUE(processes.isArray());
+    const Json::ArrayIndex processCount = processes.size();
+    for (Json::ArrayIndex i = 0; i < processCount; ++i) {
+      GET_JSON(process, processes[i], Object);
+      JSONRootCheck(process, aWithMainThread);
+    }
+  }
+
+  GET_JSON(profilingLog, aRoot["profilingLog"], Object);
+  EXPECT_EQ(profilingLog.size(), 1u);
+  for (auto it = profilingLog.begin(); it != profilingLog.end(); ++it) {
+    // The key should be a pid.
+    const auto key = it.name();
+    for (const auto letter : key) {
+      EXPECT_GE(letter, '0');
+      EXPECT_LE(letter, '9');
+    }
+    // And the value should be an object.
+    GET_JSON(logForPid, profilingLog[key], Object);
+    // Its content is not defined, but we expect at least these:
+    EXPECT_HAS_JSON(logForPid["profilingLogBegin_TSms"], Double);
+    EXPECT_HAS_JSON(logForPid["profilingLogEnd_TSms"], Double);
+  }
+}
+
+// Check that various expected top properties are in the JSON, and then call the
+// provided `aJSONCheckFunction` with the JSON root object.
+template <typename JSONCheckFunction>
+void JSONOutputCheck(const char* aOutput,
+                     JSONCheckFunction&& aJSONCheckFunction) {
+  ASSERT_NE(aOutput, nullptr);
+
+  JSONWhitespaceCheck(aOutput);
+
+  // Extract JSON.
+  Json::Value parsedRoot;
+  Json::CharReaderBuilder builder;
+  const std::unique_ptr<Json::CharReader> reader(builder.newCharReader());
+  ASSERT_TRUE(
+      reader->parse(aOutput, strchr(aOutput, '\0'), &parsedRoot, nullptr));
+
+  JSONRootCheck(parsedRoot);
+
+  std::forward<JSONCheckFunction>(aJSONCheckFunction)(parsedRoot);
+}
+
+// Returns `static_cast<SamplingState>(-1)` if callback could not be installed.
+static SamplingState WaitForSamplingState() {
+  Atomic<int> samplingState{-1};
+
+  if (!profiler_callback_after_sampling([&](SamplingState aSamplingState) {
+        samplingState = static_cast<int>(aSamplingState);
+      })) {
+    return static_cast<SamplingState>(-1);
+  }
+
+  while (samplingState == -1) {
+  }
+
+  return static_cast<SamplingState>(static_cast<int>(samplingState));
+}
+
+typedef Vector<const char*> StrVec;
+
+static void InactiveFeaturesAndParamsCheck() {
+  int entries;
+  Maybe<double> duration;
+  double interval;
+  uint32_t features;
+  StrVec filters;
+  uint64_t activeTabID;
+
+  ASSERT_TRUE(!profiler_is_active());
+  ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::MainThreadIO));
+  ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::NativeAllocations));
+
+  profiler_get_start_params(&entries, &duration, &interval, &features, &filters,
+                            &activeTabID);
+
+  ASSERT_TRUE(entries == 0);
+  ASSERT_TRUE(duration == Nothing());
+  ASSERT_TRUE(interval == 0);
+  ASSERT_TRUE(features == 0);
+  ASSERT_TRUE(filters.empty());
+  ASSERT_TRUE(activeTabID == 0);
+}
+
+static void ActiveParamsCheck(int aEntries, double aInterval,
+                              uint32_t aFeatures, const char** aFilters,
+                              size_t aFiltersLen, uint64_t aActiveTabID,
+                              const Maybe<double>& aDuration = Nothing()) {
+  int entries;
+  Maybe<double> duration;
+  double interval;
+  uint32_t features;
+  StrVec filters;
+  uint64_t activeTabID;
+
+  profiler_get_start_params(&entries, &duration, &interval, &features, &filters,
+                            &activeTabID);
+
+  ASSERT_TRUE(entries == aEntries);
+  ASSERT_TRUE(duration == aDuration);
+  ASSERT_TRUE(interval == aInterval);
+  ASSERT_TRUE(features == aFeatures);
+  ASSERT_TRUE(filters.length() == aFiltersLen);
+  ASSERT_TRUE(activeTabID == aActiveTabID);
+  for (size_t i = 0; i < aFiltersLen; i++) {
+    ASSERT_TRUE(strcmp(filters[i], aFilters[i]) == 0);
+  }
+}
+
+TEST(GeckoProfiler, FeaturesAndParams)
+{
+  InactiveFeaturesAndParamsCheck();
+
+  // Try a couple of features and filters.
+  {
+    uint32_t features = ProfilerFeature::JS;
+    const char* filters[] = {"GeckoMain", "Compositor"};
+
+#  define PROFILER_DEFAULT_DURATION 20 /* seconds, for tests only */
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 100,
+                   Some(PROFILER_DEFAULT_DURATION));
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    ActiveParamsCheck(PROFILER_DEFAULT_ENTRIES.Value(),
+                      PROFILER_DEFAULT_INTERVAL, features, filters,
+                      MOZ_ARRAY_LENGTH(filters), 100,
+                      Some(PROFILER_DEFAULT_DURATION));
+
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+  }
+
+  // Try some different features and filters.
+  {
+    uint32_t features =
+        ProfilerFeature::MainThreadIO | ProfilerFeature::IPCMessages;
+    const char* filters[] = {"GeckoMain", "Foo", "Bar"};
+
+    // Testing with some arbitrary buffer size (as could be provided by
+    // external code), which we convert to the appropriate power of 2.
+    profiler_start(PowerOfTwo32(999999), 3, features, filters,
+                   MOZ_ARRAY_LENGTH(filters), 123, Some(25.0));
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    ActiveParamsCheck(int(PowerOfTwo32(999999).Value()), 3, features, filters,
+                      MOZ_ARRAY_LENGTH(filters), 123, Some(25.0));
+
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+  }
+
+  // Try with no duration
+  {
+    uint32_t features =
+        ProfilerFeature::MainThreadIO | ProfilerFeature::IPCMessages;
+    const char* filters[] = {"GeckoMain", "Foo", "Bar"};
+
+    profiler_start(PowerOfTwo32(999999), 3, features, filters,
+                   MOZ_ARRAY_LENGTH(filters), 0, Nothing());
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    ActiveParamsCheck(int(PowerOfTwo32(999999).Value()), 3, features, filters,
+                      MOZ_ARRAY_LENGTH(filters), 0, Nothing());
+
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+  }
+
+  // Try all supported features, and filters that match all threads.
+  {
+    uint32_t availableFeatures = profiler_get_available_features();
+    const char* filters[] = {""};
+
+    profiler_start(PowerOfTwo32(88888), 10, availableFeatures, filters,
+                   MOZ_ARRAY_LENGTH(filters), 0, Some(15.0));
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    ActiveParamsCheck(PowerOfTwo32(88888).Value(), 10, availableFeatures,
+                      filters, MOZ_ARRAY_LENGTH(filters), 0, Some(15.0));
+
+    // Don't call profiler_stop() here.
+  }
+
+  // Try no features, and filters that match no threads.
+  {
+    uint32_t features = 0;
+    const char* filters[] = {"NoThreadWillMatchThis"};
+
+    // Second profiler_start() call in a row without an intervening
+    // profiler_stop(); this will do an implicit profiler_stop() and restart.
+    profiler_start(PowerOfTwo32(0), 0, features, filters,
+                   MOZ_ARRAY_LENGTH(filters), 0, Some(0.0));
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    // Entries and intervals go to defaults if 0 is specified.
+    ActiveParamsCheck(PROFILER_DEFAULT_ENTRIES.Value(),
+                      PROFILER_DEFAULT_INTERVAL, features, filters,
+                      MOZ_ARRAY_LENGTH(filters), 0, Nothing());
+
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+
+    // These calls are no-ops.
+    profiler_stop();
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+  }
+}
+
+TEST(GeckoProfiler, EnsureStarted)
+{
+  InactiveFeaturesAndParamsCheck();
+
+  uint32_t features = ProfilerFeature::JS;
+  const char* filters[] = {"GeckoMain", "Compositor"};
+  {
+    // Inactive -> Active
+    profiler_ensure_started(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                            features, filters, MOZ_ARRAY_LENGTH(filters), 0,
+                            Some(PROFILER_DEFAULT_DURATION));
+
+    ActiveParamsCheck(
+        PROFILER_DEFAULT_ENTRIES.Value(), PROFILER_DEFAULT_INTERVAL, features,
+        filters, MOZ_ARRAY_LENGTH(filters), 0, Some(PROFILER_DEFAULT_DURATION));
+  }
+
+  {
+    // Active -> Active with same settings
+
+    Maybe<ProfilerBufferInfo> info0 = profiler_get_buffer_info();
+    ASSERT_TRUE(info0->mRangeEnd > 0);
+
+    // First, write some samples into the buffer.
+    PR_Sleep(PR_MillisecondsToInterval(500));
+
+    Maybe<ProfilerBufferInfo> info1 = profiler_get_buffer_info();
+    ASSERT_TRUE(info1->mRangeEnd > info0->mRangeEnd);
+
+    // Call profiler_ensure_started with the same settings as before.
+    // This operation must not clear our buffer!
+    profiler_ensure_started(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                            features, filters, MOZ_ARRAY_LENGTH(filters), 0,
+                            Some(PROFILER_DEFAULT_DURATION));
+
+    ActiveParamsCheck(
+        PROFILER_DEFAULT_ENTRIES.Value(), PROFILER_DEFAULT_INTERVAL, features,
+        filters, MOZ_ARRAY_LENGTH(filters), 0, Some(PROFILER_DEFAULT_DURATION));
+
+    // Check that our position in the buffer stayed the same or advanced, but
+    // not by much, and the range-start after profiler_ensure_started shouldn't
+    // have passed the range-end before.
+    Maybe<ProfilerBufferInfo> info2 = profiler_get_buffer_info();
+    ASSERT_TRUE(info2->mRangeEnd >= info1->mRangeEnd);
+    ASSERT_TRUE(info2->mRangeEnd - info1->mRangeEnd <
+                info1->mRangeEnd - info0->mRangeEnd);
+    ASSERT_TRUE(info2->mRangeStart < info1->mRangeEnd);
+  }
+
+  {
+    // Active -> Active with *different* settings
+
+    Maybe<ProfilerBufferInfo> info1 = profiler_get_buffer_info();
+
+    // Call profiler_ensure_started with a different feature set than the one
+    // it's currently running with. This is supposed to stop and restart the
+    // profiler, thereby discarding the buffer contents.
+    uint32_t differentFeatures = features | ProfilerFeature::CPUUtilization;
+    profiler_ensure_started(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                            differentFeatures, filters,
+                            MOZ_ARRAY_LENGTH(filters), 0);
+
+    ActiveParamsCheck(PROFILER_DEFAULT_ENTRIES.Value(),
+                      PROFILER_DEFAULT_INTERVAL, differentFeatures, filters,
+                      MOZ_ARRAY_LENGTH(filters), 0);
+
+    // Check the the buffer was cleared, so its range-start should be at/after
+    // its range-end before.
+    Maybe<ProfilerBufferInfo> info2 = profiler_get_buffer_info();
+    ASSERT_TRUE(info2->mRangeStart >= info1->mRangeEnd);
+  }
+
+  {
+    // Active -> Inactive
+
+    profiler_stop();
+
+    InactiveFeaturesAndParamsCheck();
+  }
+}
+
+TEST(GeckoProfiler, MultiRegistration)
+{
+  // This whole test only checks that function calls don't crash, they don't
+  // actually verify that threads get profiled or not.
+
+  {
+    std::thread thread([]() {
+      char top;
+      profiler_register_thread("thread, no unreg", &top);
+    });
+    thread.join();
+  }
+
+  {
+    std::thread thread([]() { profiler_unregister_thread(); });
+    thread.join();
+  }
+
+  {
+    std::thread thread([]() {
+      char top;
+      profiler_register_thread("thread 1st", &top);
+      profiler_unregister_thread();
+      profiler_register_thread("thread 2nd", &top);
+      profiler_unregister_thread();
+    });
+    thread.join();
+  }
+
+  {
+    std::thread thread([]() {
+      char top;
+      profiler_register_thread("thread once", &top);
+      profiler_register_thread("thread again", &top);
+      profiler_unregister_thread();
+    });
+    thread.join();
+  }
+
+  {
+    std::thread thread([]() {
+      char top;
+      profiler_register_thread("thread to unreg twice", &top);
+      profiler_unregister_thread();
+      profiler_unregister_thread();
+    });
+    thread.join();
+  }
+}
+
+TEST(GeckoProfiler, DifferentThreads)
+{
+  InactiveFeaturesAndParamsCheck();
+
+  nsCOMPtr<nsIThread> thread;
+  nsresult rv = NS_NewNamedThread("GeckoProfGTest", getter_AddRefs(thread));
+  ASSERT_NS_SUCCEEDED(rv);
+
+  // Control the profiler on a background thread and verify flags on the
+  // main thread.
+  {
+    uint32_t features = ProfilerFeature::JS;
+    const char* filters[] = {"GeckoMain", "Compositor"};
+
+    thread->Dispatch(
+        NS_NewRunnableFunction("GeckoProfiler_DifferentThreads_Test::TestBody",
+                               [&]() {
+                                 profiler_start(PROFILER_DEFAULT_ENTRIES,
+                                                PROFILER_DEFAULT_INTERVAL,
+                                                features, filters,
+                                                MOZ_ARRAY_LENGTH(filters), 0);
+                               }),
+        NS_DISPATCH_SYNC);
+
+    ASSERT_TRUE(profiler_is_active());
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::MainThreadIO));
+    ASSERT_TRUE(!profiler_feature_active(ProfilerFeature::IPCMessages));
+
+    ActiveParamsCheck(PROFILER_DEFAULT_ENTRIES.Value(),
+                      PROFILER_DEFAULT_INTERVAL, features, filters,
+                      MOZ_ARRAY_LENGTH(filters), 0);
+
+    thread->Dispatch(
+        NS_NewRunnableFunction("GeckoProfiler_DifferentThreads_Test::TestBody",
+                               [&]() { profiler_stop(); }),
+        NS_DISPATCH_SYNC);
+
+    InactiveFeaturesAndParamsCheck();
+  }
+
+  // Control the profiler on the main thread and verify flags on a
+  // background thread.
+  {
+    uint32_t features = ProfilerFeature::JS;
+    const char* filters[] = {"GeckoMain", "Compositor"};
+
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+    thread->Dispatch(
+        NS_NewRunnableFunction(
+            "GeckoProfiler_DifferentThreads_Test::TestBody",
+            [&]() {
+              ASSERT_TRUE(profiler_is_active());
+              ASSERT_TRUE(
+                  !profiler_feature_active(ProfilerFeature::MainThreadIO));
+              ASSERT_TRUE(
+                  !profiler_feature_active(ProfilerFeature::IPCMessages));
+
+              ActiveParamsCheck(PROFILER_DEFAULT_ENTRIES.Value(),
+                                PROFILER_DEFAULT_INTERVAL, features, filters,
+                                MOZ_ARRAY_LENGTH(filters), 0);
+            }),
+        NS_DISPATCH_SYNC);
+
+    profiler_stop();
+
+    thread->Dispatch(
+        NS_NewRunnableFunction("GeckoProfiler_DifferentThreads_Test::TestBody",
+                               [&]() { InactiveFeaturesAndParamsCheck(); }),
+        NS_DISPATCH_SYNC);
+  }
+
+  thread->Shutdown();
+}
+
+TEST(GeckoProfiler, GetBacktrace)
+{
+  ASSERT_TRUE(!profiler_get_backtrace());
+
+  {
+    uint32_t features = ProfilerFeature::StackWalk;
+    const char* filters[] = {"GeckoMain"};
+
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+    // These will be destroyed while the profiler is active.
+    static const int N = 100;
+    {
+      UniqueProfilerBacktrace u[N];
+      for (int i = 0; i < N; i++) {
+        u[i] = profiler_get_backtrace();
+        ASSERT_TRUE(u[i]);
+      }
+    }
+
+    // These will be destroyed after the profiler stops.
+    UniqueProfilerBacktrace u[N];
+    for (int i = 0; i < N; i++) {
+      u[i] = profiler_get_backtrace();
+      ASSERT_TRUE(u[i]);
+    }
+
+    profiler_stop();
+  }
+
+  ASSERT_TRUE(!profiler_get_backtrace());
+}
+
+TEST(GeckoProfiler, Pause)
+{
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test must run on the main thread";
+
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain", "Profiled GeckoProfiler.Pause"};
+
+  ASSERT_TRUE(!profiler_is_paused());
+  for (ThreadProfilingFeatures features : scEachAndAnyThreadProfilingFeatures) {
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+    ASSERT_TRUE(
+        !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(profiler_current_thread_id(),
+                                                   features));
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                   features));
+  }
+
+  std::thread{[&]() {
+    {
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Ignored GeckoProfiler.Pause - before start");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Profiled GeckoProfiler.Pause - before start");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+  }}.join();
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  ASSERT_TRUE(!profiler_is_paused());
+  for (ThreadProfilingFeatures features : scEachAndAnyThreadProfilingFeatures) {
+    ASSERT_TRUE(profiler_thread_is_being_profiled(features));
+    ASSERT_TRUE(
+        profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+    ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_current_thread_id(),
+                                                  features));
+  }
+
+  std::thread{[&]() {
+    {
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Ignored GeckoProfiler.Pause - after start");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Profiled GeckoProfiler.Pause - after start");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+  }}.join();
+
+  // Check that we are writing samples while not paused.
+  Maybe<ProfilerBufferInfo> info1 = profiler_get_buffer_info();
+  PR_Sleep(PR_MillisecondsToInterval(500));
+  Maybe<ProfilerBufferInfo> info2 = profiler_get_buffer_info();
+  ASSERT_TRUE(info1->mRangeEnd != info2->mRangeEnd);
+
+  // Check that we are writing markers while not paused.
+  ASSERT_TRUE(profiler_thread_is_being_profiled_for_markers());
+  ASSERT_TRUE(
+      profiler_thread_is_being_profiled_for_markers(ProfilerThreadId{}));
+  ASSERT_TRUE(profiler_thread_is_being_profiled_for_markers(
+      profiler_current_thread_id()));
+  ASSERT_TRUE(
+      profiler_thread_is_being_profiled_for_markers(profiler_main_thread_id()));
+  info1 = profiler_get_buffer_info();
+  PROFILER_MARKER_UNTYPED("Not paused", OTHER, {});
+  info2 = profiler_get_buffer_info();
+  ASSERT_TRUE(info1->mRangeEnd != info2->mRangeEnd);
+
+  profiler_pause();
+
+  ASSERT_TRUE(profiler_is_paused());
+  for (ThreadProfilingFeatures features : scEachAndAnyThreadProfilingFeatures) {
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+    ASSERT_TRUE(
+        !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(profiler_current_thread_id(),
+                                                   features));
+  }
+  ASSERT_TRUE(!profiler_thread_is_being_profiled_for_markers());
+  ASSERT_TRUE(
+      !profiler_thread_is_being_profiled_for_markers(ProfilerThreadId{}));
+  ASSERT_TRUE(!profiler_thread_is_being_profiled_for_markers(
+      profiler_current_thread_id()));
+  ASSERT_TRUE(!profiler_thread_is_being_profiled_for_markers(
+      profiler_main_thread_id()));
+
+  std::thread{[&]() {
+    {
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Ignored GeckoProfiler.Pause - after pause");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Profiled GeckoProfiler.Pause - after pause");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+  }}.join();
+
+  // Check that we are not writing samples while paused.
+  info1 = profiler_get_buffer_info();
+  PR_Sleep(PR_MillisecondsToInterval(500));
+  info2 = profiler_get_buffer_info();
+  ASSERT_TRUE(info1->mRangeEnd == info2->mRangeEnd);
+
+  // Check that we are now writing markers while paused.
+  info1 = profiler_get_buffer_info();
+  PROFILER_MARKER_UNTYPED("Paused", OTHER, {});
+  info2 = profiler_get_buffer_info();
+  ASSERT_TRUE(info1->mRangeEnd == info2->mRangeEnd);
+  PROFILER_MARKER_UNTYPED("Paused v2", OTHER, {});
+  Maybe<ProfilerBufferInfo> info3 = profiler_get_buffer_info();
+  ASSERT_TRUE(info2->mRangeEnd == info3->mRangeEnd);
+
+  profiler_resume();
+
+  ASSERT_TRUE(!profiler_is_paused());
+  for (ThreadProfilingFeatures features : scEachAndAnyThreadProfilingFeatures) {
+    ASSERT_TRUE(profiler_thread_is_being_profiled(features));
+    ASSERT_TRUE(
+        profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+    ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_current_thread_id(),
+                                                  features));
+  }
+
+  std::thread{[&]() {
+    {
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Ignored GeckoProfiler.Pause - after resume");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Profiled GeckoProfiler.Pause - after resume");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(profiler_thread_is_being_profiled(profiler_main_thread_id(),
+                                                      features));
+      }
+    }
+  }}.join();
+
+  profiler_stop();
+
+  ASSERT_TRUE(!profiler_is_paused());
+  for (ThreadProfilingFeatures features : scEachAndAnyThreadProfilingFeatures) {
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+    ASSERT_TRUE(
+        !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+    ASSERT_TRUE(!profiler_thread_is_being_profiled(profiler_current_thread_id(),
+                                                   features));
+  }
+
+  std::thread{[&]() {
+    {
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD("Ignored GeckoProfiler.Pause - after stop");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+    {
+      AUTO_PROFILER_REGISTER_THREAD(
+          "Profiled GeckoProfiler.Pause - after stop");
+      for (ThreadProfilingFeatures features :
+           scEachAndAnyThreadProfilingFeatures) {
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(features));
+        ASSERT_TRUE(
+            !profiler_thread_is_being_profiled(ProfilerThreadId{}, features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_current_thread_id(), features));
+        ASSERT_TRUE(!profiler_thread_is_being_profiled(
+            profiler_main_thread_id(), features));
+      }
+    }
+  }}.join();
+}
+
+TEST(GeckoProfiler, Markers)
+{
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  PROFILER_MARKER("tracing event", OTHER, {}, Tracing, "A");
+  PROFILER_MARKER("tracing start", OTHER, MarkerTiming::IntervalStart(),
+                  Tracing, "A");
+  PROFILER_MARKER("tracing end", OTHER, MarkerTiming::IntervalEnd(), Tracing,
+                  "A");
+
+  auto bt = profiler_capture_backtrace();
+  PROFILER_MARKER("tracing event with stack", OTHER,
+                  MarkerStack::TakeBacktrace(std::move(bt)), Tracing, "B");
+
+  { AUTO_PROFILER_TRACING_MARKER("C", "auto tracing", OTHER); }
+
+  PROFILER_MARKER_UNTYPED("M1", OTHER, {});
+  PROFILER_MARKER_UNTYPED("M3", OTHER, {});
+
+  // Create three strings: two that are the maximum allowed length, and one that
+  // is one char longer.
+  static const size_t kMax = ProfileBuffer::kMaxFrameKeyLength;
+  UniquePtr<char[]> okstr1 = MakeUnique<char[]>(kMax);
+  UniquePtr<char[]> okstr2 = MakeUnique<char[]>(kMax);
+  UniquePtr<char[]> longstr = MakeUnique<char[]>(kMax + 1);
+  UniquePtr<char[]> longstrCut = MakeUnique<char[]>(kMax + 1);
+  for (size_t i = 0; i < kMax; i++) {
+    okstr1[i] = 'a';
+    okstr2[i] = 'b';
+    longstr[i] = 'c';
+    longstrCut[i] = 'c';
+  }
+  okstr1[kMax - 1] = '\0';
+  okstr2[kMax - 1] = '\0';
+  longstr[kMax] = '\0';
+  longstrCut[kMax] = '\0';
+  // Should be output as-is.
+  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("", LAYOUT, "");
+  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("", LAYOUT, okstr1.get());
+  // Should be output as label + space + okstr2.
+  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("okstr2", LAYOUT, okstr2.get());
+  // Should be output with kMax length, ending with "...\0".
+  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("", LAYOUT, longstr.get());
+  ASSERT_EQ(longstrCut[kMax - 4], 'c');
+  longstrCut[kMax - 4] = '.';
+  ASSERT_EQ(longstrCut[kMax - 3], 'c');
+  longstrCut[kMax - 3] = '.';
+  ASSERT_EQ(longstrCut[kMax - 2], 'c');
+  longstrCut[kMax - 2] = '.';
+  ASSERT_EQ(longstrCut[kMax - 1], 'c');
+  longstrCut[kMax - 1] = '\0';
+
+  // Test basic markers 2.0.
+  EXPECT_TRUE(
+      profiler_add_marker("default-templated markers 2.0 with empty options",
+                          geckoprofiler::category::OTHER, {}));
+
+  PROFILER_MARKER_UNTYPED(
+      "default-templated markers 2.0 with option", OTHER,
+      MarkerStack::TakeBacktrace(profiler_capture_backtrace()));
+
+  PROFILER_MARKER("explicitly-default-templated markers 2.0 with empty options",
+                  OTHER, {}, NoPayload);
+
+  EXPECT_TRUE(profiler_add_marker(
+      "explicitly-default-templated markers 2.0 with option",
+      geckoprofiler::category::OTHER, {},
+      ::geckoprofiler::markers::NoPayload{}));
+
+  // Used in markers below.
+  TimeStamp ts1 = TimeStamp::Now();
+
+  // Sleep briefly to ensure a sample is taken and the pending markers are
+  // processed.
+  PR_Sleep(PR_MillisecondsToInterval(500));
+
+  // Used in markers below.
+  TimeStamp ts2 = TimeStamp::Now();
+  // ts1 and ts2 should be different thanks to the sleep.
+  EXPECT_NE(ts1, ts2);
+
+  // Test most marker payloads.
+
+  // Keep this one first! (It's used to record `ts1` and `ts2`, to compare
+  // to serialized numbers in other markers.)
+  EXPECT_TRUE(profiler_add_marker("FirstMarker", geckoprofiler::category::OTHER,
+                                  MarkerTiming::Interval(ts1, ts2),
+                                  geckoprofiler::markers::TextMarker{},
+                                  "First Marker"));
+
+  // User-defined marker type with different properties, and fake schema.
+  struct GtestMarker {
+    static constexpr Span<const char> MarkerTypeName() {
+      return MakeStringSpan("markers-gtest");
+    }
+    static void StreamJSONMarkerData(
+        mozilla::baseprofiler::SpliceableJSONWriter& aWriter, int aInt,
+        double aDouble, const mozilla::ProfilerString8View& aText,
+        const mozilla::ProfilerString8View& aUniqueText,
+        const mozilla::TimeStamp& aTime) {
+      aWriter.NullProperty("null");
+      aWriter.BoolProperty("bool-false", false);
+      aWriter.BoolProperty("bool-true", true);
+      aWriter.IntProperty("int", aInt);
+      aWriter.DoubleProperty("double", aDouble);
+      aWriter.StringProperty("text", aText);
+      aWriter.UniqueStringProperty("unique text", aUniqueText);
+      aWriter.UniqueStringProperty("unique text again", aUniqueText);
+      aWriter.TimeProperty("time", aTime);
+    }
+    static mozilla::MarkerSchema MarkerTypeDisplay() {
+      // Note: This is an test function that is not intended to actually output
+      // that correctly matches StreamJSONMarkerData data above! Instead we only
+      // test that it outputs the expected JSON at the end.
+      using MS = mozilla::MarkerSchema;
+      MS schema{MS::Location::MarkerChart,      MS::Location::MarkerTable,
+                MS::Location::TimelineOverview, MS::Location::TimelineMemory,
+                MS::Location::TimelineIPC,      MS::Location::TimelineFileIO,
+                MS::Location::StackChart};
+      // All label functions.
+      schema.SetChartLabel("chart label");
+      schema.SetTooltipLabel("tooltip label");
+      schema.SetTableLabel("table label");
+      // All data functions, all formats, all "searchable" values.
+      schema.AddKeyFormat("key with url", MS::Format::Url);
+      schema.AddKeyLabelFormat("key with label filePath", "label filePath",
+                               MS::Format::FilePath);
+      schema.AddKeyFormatSearchable("key with string not-searchable",
+                                    MS::Format::String,
+                                    MS::Searchable::NotSearchable);
+      schema.AddKeyLabelFormatSearchable("key with label duration searchable",
+                                         "label duration", MS::Format::Duration,
+                                         MS::Searchable::Searchable);
+      schema.AddKeyFormat("key with time", MS::Format::Time);
+      schema.AddKeyFormat("key with seconds", MS::Format::Seconds);
+      schema.AddKeyFormat("key with milliseconds", MS::Format::Milliseconds);
+      schema.AddKeyFormat("key with microseconds", MS::Format::Microseconds);
+      schema.AddKeyFormat("key with nanoseconds", MS::Format::Nanoseconds);
+      schema.AddKeyFormat("key with bytes", MS::Format::Bytes);
+      schema.AddKeyFormat("key with percentage", MS::Format::Percentage);
+      schema.AddKeyFormat("key with integer", MS::Format::Integer);
+      schema.AddKeyFormat("key with decimal", MS::Format::Decimal);
+      schema.AddStaticLabelValue("static label", "static value");
+      return schema;
+    }
+  };
+  EXPECT_TRUE(
+      profiler_add_marker("Gtest custom marker", geckoprofiler::category::OTHER,
+                          MarkerTiming::Interval(ts1, ts2), GtestMarker{}, 42,
+                          43.0, "gtest text", "gtest unique text", ts1));
+
+  // User-defined marker type with no data, special frontend schema.
+  struct GtestSpecialMarker {
+    static constexpr Span<const char> MarkerTypeName() {
+      return MakeStringSpan("markers-gtest-special");
+    }
+    static void StreamJSONMarkerData(
+        mozilla::baseprofiler::SpliceableJSONWriter& aWriter) {}
+    static mozilla::MarkerSchema MarkerTypeDisplay() {
+      return mozilla::MarkerSchema::SpecialFrontendLocation{};
+    }
+  };
+  EXPECT_TRUE(profiler_add_marker("Gtest special marker",
+                                  geckoprofiler::category::OTHER, {},
+                                  GtestSpecialMarker{}));
+
+  // User-defined marker type that is never used, so it shouldn't appear in the
+  // output.
+  struct GtestUnusedMarker {
+    static constexpr Span<const char> MarkerTypeName() {
+      return MakeStringSpan("markers-gtest-unused");
+    }
+    static void StreamJSONMarkerData(
+        mozilla::baseprofiler::SpliceableJSONWriter& aWriter) {}
+    static mozilla::MarkerSchema MarkerTypeDisplay() {
+      return mozilla::MarkerSchema::SpecialFrontendLocation{};
+    }
+  };
+
+  // Make sure the compiler doesn't complain about this unused struct.
+  mozilla::Unused << GtestUnusedMarker{};
+
+  // Other markers in alphabetical order of payload class names.
+
+  nsCOMPtr<nsIURI> uri;
+  ASSERT_TRUE(
+      NS_SUCCEEDED(NS_NewURI(getter_AddRefs(uri), "http://mozilla.org/"_ns)));
+  // The marker name will be "Load <aChannelId>: <aURI>".
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 1,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_START,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheHit,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      /* nsIURI* aRedirectURI = nullptr */
+      /* uint64_t aRedirectChannelId = 0 */
+  );
+
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 2,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_STOP,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false,
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */ nullptr,
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      nullptr,
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      Some(nsDependentCString("text/html")),
+      /* nsIURI* aRedirectURI = nullptr */ nullptr,
+      /* uint64_t aRedirectChannelId = 0 */ 0);
+
+  nsCOMPtr<nsIURI> redirectURI;
+  ASSERT_TRUE(NS_SUCCEEDED(
+      NS_NewURI(getter_AddRefs(redirectURI), "http://example.com/"_ns)));
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 3,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_REDIRECT,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false,
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */ nullptr,
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      nullptr,
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      mozilla::Nothing(),
+      /* nsIURI* aRedirectURI = nullptr */ redirectURI,
+      /* uint32_t aRedirectFlags = 0 */
+      nsIChannelEventSink::REDIRECT_TEMPORARY,
+      /* uint64_t aRedirectChannelId = 0 */ 103);
+
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 4,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_REDIRECT,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false,
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */ nullptr,
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      nullptr,
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      mozilla::Nothing(),
+      /* nsIURI* aRedirectURI = nullptr */ redirectURI,
+      /* uint32_t aRedirectFlags = 0 */
+      nsIChannelEventSink::REDIRECT_PERMANENT,
+      /* uint64_t aRedirectChannelId = 0 */ 104);
+
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 5,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_REDIRECT,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false,
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */ nullptr,
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      nullptr,
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      mozilla::Nothing(),
+      /* nsIURI* aRedirectURI = nullptr */ redirectURI,
+      /* uint32_t aRedirectFlags = 0 */ nsIChannelEventSink::REDIRECT_INTERNAL,
+      /* uint64_t aRedirectChannelId = 0 */ 105);
+
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 6,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_REDIRECT,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ false,
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */ nullptr,
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      nullptr,
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      mozilla::Nothing(),
+      /* nsIURI* aRedirectURI = nullptr */ redirectURI,
+      /* uint32_t aRedirectFlags = 0 */ nsIChannelEventSink::REDIRECT_INTERNAL |
+          nsIChannelEventSink::REDIRECT_STS_UPGRADE,
+      /* uint64_t aRedirectChannelId = 0 */ 106);
+  profiler_add_network_marker(
+      /* nsIURI* aURI */ uri,
+      /* const nsACString& aRequestMethod */ "GET"_ns,
+      /* int32_t aPriority */ 34,
+      /* uint64_t aChannelId */ 7,
+      /* NetworkLoadType aType */ net::NetworkLoadType::LOAD_START,
+      /* mozilla::TimeStamp aStart */ ts1,
+      /* mozilla::TimeStamp aEnd */ ts2,
+      /* int64_t aCount */ 56,
+      /* mozilla::net::CacheDisposition aCacheDisposition */
+      net::kCacheUnresolved,
+      /* uint64_t aInnerWindowID */ 78,
+      /* bool aIsPrivateBrowsing */ true
+      /* const mozilla::net::TimingStruct* aTimings = nullptr */
+      /* mozilla::UniquePtr<mozilla::ProfileChunkedBuffer> aSource =
+         nullptr */
+      /* const mozilla::Maybe<nsDependentCString>& aContentType =
+         mozilla::Nothing() */
+      /* nsIURI* aRedirectURI = nullptr */
+      /* uint64_t aRedirectChannelId = 0 */
+  );
+
+  EXPECT_TRUE(profiler_add_marker(
+      "Text in main thread with stack", geckoprofiler::category::OTHER,
+      {MarkerStack::Capture(), MarkerTiming::Interval(ts1, ts2)},
+      geckoprofiler::markers::TextMarker{}, ""));
+  EXPECT_TRUE(profiler_add_marker(
+      "Text from main thread with stack", geckoprofiler::category::OTHER,
+      MarkerOptions(MarkerThreadId::MainThread(), MarkerStack::Capture()),
+      geckoprofiler::markers::TextMarker{}, ""));
+
+  std::thread registeredThread([]() {
+    AUTO_PROFILER_REGISTER_THREAD("Marker test sub-thread");
+    // Marker in non-profiled thread won't be stored.
+    EXPECT_FALSE(profiler_add_marker(
+        "Text in registered thread with stack", geckoprofiler::category::OTHER,
+        MarkerStack::Capture(), geckoprofiler::markers::TextMarker{}, ""));
+    // Marker will be stored in main thread, with stack from registered thread.
+    EXPECT_TRUE(profiler_add_marker(
+        "Text from registered thread with stack",
+        geckoprofiler::category::OTHER,
+        MarkerOptions(MarkerThreadId::MainThread(), MarkerStack::Capture()),
+        geckoprofiler::markers::TextMarker{}, ""));
+  });
+  registeredThread.join();
+
+  std::thread unregisteredThread([]() {
+    // Marker in unregistered thread won't be stored.
+    EXPECT_FALSE(profiler_add_marker("Text in unregistered thread with stack",
+                                     geckoprofiler::category::OTHER,
+                                     MarkerStack::Capture(),
+                                     geckoprofiler::markers::TextMarker{}, ""));
+    // Marker will be stored in main thread, but stack cannot be captured in an
+    // unregistered thread.
+    EXPECT_TRUE(profiler_add_marker(
+        "Text from unregistered thread with stack",
+        geckoprofiler::category::OTHER,
+        MarkerOptions(MarkerThreadId::MainThread(), MarkerStack::Capture()),
+        geckoprofiler::markers::TextMarker{}, ""));
+  });
+  unregisteredThread.join();
+
+  EXPECT_TRUE(profiler_add_marker("Tracing", geckoprofiler::category::OTHER, {},
+                                  geckoprofiler::markers::Tracing{},
+                                  "category"));
+
+  EXPECT_TRUE(profiler_add_marker("Text", geckoprofiler::category::OTHER, {},
+                                  geckoprofiler::markers::TextMarker{},
+                                  "Text text"));
+
+  EXPECT_TRUE(profiler_add_marker(
+      "MediaSample", geckoprofiler::category::OTHER, {},
+      geckoprofiler::markers::MediaSampleMarker{}, 123, 456, 789));
+
+  SpliceableChunkedJSONWriter w{FailureLatchInfallibleSource::Singleton()};
+  w.Start();
+  EXPECT_TRUE(::profiler_stream_json_for_this_process(w));
+  w.End();
+
+  EXPECT_FALSE(w.Failed());
+
+  UniquePtr<char[]> profile = w.ChunkedWriteFunc().CopyData();
+  ASSERT_TRUE(!!profile.get());
+
+  // Expected markers, in order.
+  enum State {
+    S_tracing_event,
+    S_tracing_start,
+    S_tracing_end,
+    S_tracing_event_with_stack,
+    S_tracing_auto_tracing_start,
+    S_tracing_auto_tracing_end,
+    S_M1,
+    S_M3,
+    S_Markers2DefaultEmptyOptions,
+    S_Markers2DefaultWithOptions,
+    S_Markers2ExplicitDefaultEmptyOptions,
+    S_Markers2ExplicitDefaultWithOptions,
+    S_FirstMarker,
+    S_CustomMarker,
+    S_SpecialMarker,
+    S_NetworkMarkerPayload_start,
+    S_NetworkMarkerPayload_stop,
+    S_NetworkMarkerPayload_redirect_temporary,
+    S_NetworkMarkerPayload_redirect_permanent,
+    S_NetworkMarkerPayload_redirect_internal,
+    S_NetworkMarkerPayload_redirect_internal_sts,
+    S_NetworkMarkerPayload_private_browsing,
+
+    S_TextWithStack,
+    S_TextToMTWithStack,
+    S_RegThread_TextToMTWithStack,
+    S_UnregThread_TextToMTWithStack,
+
+    S_LAST,
+  } state = State(0);
+
+  // These will be set when first read from S_FirstMarker, then
+  // compared in following markers.
+  // TODO: Compute these values from the timestamps.
+  double ts1Double = 0.0;
+  double ts2Double = 0.0;
+
+  JSONOutputCheck(profile.get(), [&](const Json::Value& root) {
+    {
+      GET_JSON(threads, root["threads"], Array);
+      ASSERT_EQ(threads.size(), 1u);
+
+      {
+        GET_JSON(thread0, threads[0], Object);
+
+        // Keep a reference to the string table in this block, it will be used
+        // below.
+        GET_JSON(stringTable, thread0["stringTable"], Array);
+        ASSERT_TRUE(stringTable.isArray());
+
+        // Test the expected labels in the string table.
+        bool foundEmpty = false;
+        bool foundOkstr1 = false;
+        bool foundOkstr2 = false;
+        const std::string okstr2Label = std::string("okstr2 ") + okstr2.get();
+        bool foundTooLong = false;
+        for (const auto& s : stringTable) {
+          ASSERT_TRUE(s.isString());
+          std::string sString = s.asString();
+          if (sString.empty()) {
+            EXPECT_FALSE(foundEmpty);
+            foundEmpty = true;
+          } else if (sString == okstr1.get()) {
+            EXPECT_FALSE(foundOkstr1);
+            foundOkstr1 = true;
+          } else if (sString == okstr2Label) {
+            EXPECT_FALSE(foundOkstr2);
+            foundOkstr2 = true;
+          } else if (sString == longstrCut.get()) {
+            EXPECT_FALSE(foundTooLong);
+            foundTooLong = true;
+          } else {
+            EXPECT_NE(sString, longstr.get());
+          }
+        }
+        EXPECT_TRUE(foundEmpty);
+        EXPECT_TRUE(foundOkstr1);
+        EXPECT_TRUE(foundOkstr2);
+        EXPECT_TRUE(foundTooLong);
+
+        {
+          GET_JSON(markers, thread0["markers"], Object);
+
+          {
+            GET_JSON(data, markers["data"], Array);
+
+            for (const Json::Value& marker : data) {
+              // Name the indexes into the marker tuple:
+              // [name, startTime, endTime, phase, category, payload]
+              const unsigned int NAME = 0u;
+              const unsigned int START_TIME = 1u;
+              const unsigned int END_TIME = 2u;
+              const unsigned int PHASE = 3u;
+              const unsigned int CATEGORY = 4u;
+              const unsigned int PAYLOAD = 5u;
+
+              const unsigned int PHASE_INSTANT = 0;
+              const unsigned int PHASE_INTERVAL = 1;
+              const unsigned int PHASE_START = 2;
+              const unsigned int PHASE_END = 3;
+
+              const unsigned int SIZE_WITHOUT_PAYLOAD = 5u;
+              const unsigned int SIZE_WITH_PAYLOAD = 6u;
+
+              ASSERT_TRUE(marker.isArray());
+              // The payload is optional.
+              ASSERT_GE(marker.size(), SIZE_WITHOUT_PAYLOAD);
+              ASSERT_LE(marker.size(), SIZE_WITH_PAYLOAD);
+
+              // root.threads[0].markers.data[i] is an array with 5 or 6
+              // elements.
+
+              ASSERT_TRUE(marker[NAME].isUInt());  // name id
+              GET_JSON(name, stringTable[marker[NAME].asUInt()], String);
+              std::string nameString = name.asString();
+
+              EXPECT_TRUE(marker[START_TIME].isNumeric());
+              EXPECT_TRUE(marker[END_TIME].isNumeric());
+              EXPECT_TRUE(marker[PHASE].isUInt());
+              EXPECT_TRUE(marker[PHASE].asUInt() < 4);
+              EXPECT_TRUE(marker[CATEGORY].isUInt());
+
+#  define EXPECT_TIMING_INSTANT                  \
+    EXPECT_NE(marker[START_TIME].asDouble(), 0); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), 0);   \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_INSTANT);
+#  define EXPECT_TIMING_INTERVAL                 \
+    EXPECT_NE(marker[START_TIME].asDouble(), 0); \
+    EXPECT_NE(marker[END_TIME].asDouble(), 0);   \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_INTERVAL);
+#  define EXPECT_TIMING_START                    \
+    EXPECT_NE(marker[START_TIME].asDouble(), 0); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), 0);   \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_START);
+#  define EXPECT_TIMING_END                      \
+    EXPECT_EQ(marker[START_TIME].asDouble(), 0); \
+    EXPECT_NE(marker[END_TIME].asDouble(), 0);   \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_END);
+
+#  define EXPECT_TIMING_INSTANT_AT(t)            \
+    EXPECT_EQ(marker[START_TIME].asDouble(), t); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), 0);   \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_INSTANT);
+#  define EXPECT_TIMING_INTERVAL_AT(start, end)      \
+    EXPECT_EQ(marker[START_TIME].asDouble(), start); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), end);     \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_INTERVAL);
+#  define EXPECT_TIMING_START_AT(start)              \
+    EXPECT_EQ(marker[START_TIME].asDouble(), start); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), 0);       \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_START);
+#  define EXPECT_TIMING_END_AT(end)              \
+    EXPECT_EQ(marker[START_TIME].asDouble(), 0); \
+    EXPECT_EQ(marker[END_TIME].asDouble(), end); \
+    EXPECT_EQ(marker[PHASE].asUInt(), PHASE_END);
+
+              if (marker.size() == SIZE_WITHOUT_PAYLOAD) {
+                // root.threads[0].markers.data[i] is an array with 5 elements,
+                // so there is no payload.
+                if (nameString == "M1") {
+                  ASSERT_EQ(state, S_M1);
+                  state = State(state + 1);
+                } else if (nameString == "M3") {
+                  ASSERT_EQ(state, S_M3);
+                  state = State(state + 1);
+                } else if (nameString ==
+                           "default-templated markers 2.0 with empty options") {
+                  EXPECT_EQ(state, S_Markers2DefaultEmptyOptions);
+                  state = State(S_Markers2DefaultEmptyOptions + 1);
+// TODO: Re-enable this when bug 1646714 lands, and check for stack.
+#  if 0
+              } else if (nameString ==
+                         "default-templated markers 2.0 with option") {
+                EXPECT_EQ(state, S_Markers2DefaultWithOptions);
+                state = State(S_Markers2DefaultWithOptions + 1);
+#  endif
+                } else if (nameString ==
+                           "explicitly-default-templated markers 2.0 with "
+                           "empty "
+                           "options") {
+                  EXPECT_EQ(state, S_Markers2ExplicitDefaultEmptyOptions);
+                  state = State(S_Markers2ExplicitDefaultEmptyOptions + 1);
+                } else if (nameString ==
+                           "explicitly-default-templated markers 2.0 with "
+                           "option") {
+                  EXPECT_EQ(state, S_Markers2ExplicitDefaultWithOptions);
+                  state = State(S_Markers2ExplicitDefaultWithOptions + 1);
+                }
+              } else {
+                // root.threads[0].markers.data[i] is an array with 6 elements,
+                // so there is a payload.
+                GET_JSON(payload, marker[PAYLOAD], Object);
+
+                // root.threads[0].markers.data[i][PAYLOAD] is an object
+                // (payload).
+
+                // It should at least have a "type" string.
+                GET_JSON(type, payload["type"], String);
+                std::string typeString = type.asString();
+
+                if (nameString == "tracing event") {
+                  EXPECT_EQ(state, S_tracing_event);
+                  state = State(S_tracing_event + 1);
+                  EXPECT_EQ(typeString, "tracing");
+                  EXPECT_TIMING_INSTANT;
+                  EXPECT_EQ_JSON(payload["category"], String, "A");
+                  EXPECT_TRUE(payload["stack"].isNull());
+
+                } else if (nameString == "tracing start") {
+                  EXPECT_EQ(state, S_tracing_start);
+                  state = State(S_tracing_start + 1);
+                  EXPECT_EQ(typeString, "tracing");
+                  EXPECT_TIMING_START;
+                  EXPECT_EQ_JSON(payload["category"], String, "A");
+                  EXPECT_TRUE(payload["stack"].isNull());
+
+                } else if (nameString == "tracing end") {
+                  EXPECT_EQ(state, S_tracing_end);
+                  state = State(S_tracing_end + 1);
+                  EXPECT_EQ(typeString, "tracing");
+                  EXPECT_TIMING_END;
+                  EXPECT_EQ_JSON(payload["category"], String, "A");
+                  EXPECT_TRUE(payload["stack"].isNull());
+
+                } else if (nameString == "tracing event with stack") {
+                  EXPECT_EQ(state, S_tracing_event_with_stack);
+                  state = State(S_tracing_event_with_stack + 1);
+                  EXPECT_EQ(typeString, "tracing");
+                  EXPECT_TIMING_INSTANT;
+                  EXPECT_EQ_JSON(payload["category"], String, "B");
+                  EXPECT_TRUE(payload["stack"].isObject());
+
+                } else if (nameString == "auto tracing") {
+                  switch (state) {
+                    case S_tracing_auto_tracing_start:
+                      state = State(S_tracing_auto_tracing_start + 1);
+                      EXPECT_EQ(typeString, "tracing");
+                      EXPECT_TIMING_START;
+                      EXPECT_EQ_JSON(payload["category"], String, "C");
+                      EXPECT_TRUE(payload["stack"].isNull());
+                      break;
+                    case S_tracing_auto_tracing_end:
+                      state = State(S_tracing_auto_tracing_end + 1);
+                      EXPECT_EQ(typeString, "tracing");
+                      EXPECT_TIMING_END;
+                      EXPECT_EQ_JSON(payload["category"], String, "C");
+                      ASSERT_TRUE(payload["stack"].isNull());
+                      break;
+                    default:
+                      EXPECT_TRUE(state == S_tracing_auto_tracing_start ||
+                                  state == S_tracing_auto_tracing_end);
+                      break;
+                  }
+
+                } else if (nameString ==
+                           "default-templated markers 2.0 with option") {
+                  // TODO: Remove this when bug 1646714 lands.
+                  EXPECT_EQ(state, S_Markers2DefaultWithOptions);
+                  state = State(S_Markers2DefaultWithOptions + 1);
+                  EXPECT_EQ(typeString, "NoPayloadUserData");
+                  EXPECT_FALSE(payload["stack"].isNull());
+
+                } else if (nameString == "FirstMarker") {
+                  // Record start and end times, to compare with timestamps in
+                  // following markers.
+                  EXPECT_EQ(state, S_FirstMarker);
+                  ts1Double = marker[START_TIME].asDouble();
+                  ts2Double = marker[END_TIME].asDouble();
+                  state = State(S_FirstMarker + 1);
+                  EXPECT_EQ(typeString, "Text");
+                  EXPECT_EQ_JSON(payload["name"], String, "First Marker");
+
+                } else if (nameString == "Gtest custom marker") {
+                  EXPECT_EQ(state, S_CustomMarker);
+                  state = State(S_CustomMarker + 1);
+                  EXPECT_EQ(typeString, "markers-gtest");
+                  EXPECT_EQ(payload.size(), 1u + 9u);
+                  EXPECT_TRUE(payload["null"].isNull());
+                  EXPECT_EQ_JSON(payload["bool-false"], Bool, false);
+                  EXPECT_EQ_JSON(payload["bool-true"], Bool, true);
+                  EXPECT_EQ_JSON(payload["int"], Int64, 42);
+                  EXPECT_EQ_JSON(payload["double"], Double, 43.0);
+                  EXPECT_EQ_JSON(payload["text"], String, "gtest text");
+                  // Unique strings can be fetched from the string table.
+                  ASSERT_TRUE(payload["unique text"].isUInt());
+                  auto textIndex = payload["unique text"].asUInt();
+                  GET_JSON(uniqueText, stringTable[textIndex], String);
+                  ASSERT_TRUE(uniqueText.isString());
+                  ASSERT_EQ(uniqueText.asString(), "gtest unique text");
+                  // The duplicate unique text should have the exact same index.
+                  EXPECT_EQ_JSON(payload["unique text again"], UInt, textIndex);
+                  EXPECT_EQ_JSON(payload["time"], Double, ts1Double);
+
+                } else if (nameString == "Gtest special marker") {
+                  EXPECT_EQ(state, S_SpecialMarker);
+                  state = State(S_SpecialMarker + 1);
+                  EXPECT_EQ(typeString, "markers-gtest-special");
+                  EXPECT_EQ(payload.size(), 1u) << "Only 'type' in the payload";
+
+                } else if (nameString == "Load 1: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_start);
+                  state = State(S_NetworkMarkerPayload_start + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 1);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Hit");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_TRUE(payload["RedirectURI"].isNull());
+                  EXPECT_TRUE(payload["redirectType"].isNull());
+                  EXPECT_TRUE(payload["isHttpToHttpsRedirect"].isNull());
+                  EXPECT_TRUE(payload["redirectId"].isNull());
+                  EXPECT_TRUE(payload["contentType"].isNull());
+
+                } else if (nameString == "Load 2: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_stop);
+                  state = State(S_NetworkMarkerPayload_stop + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 2);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_TRUE(payload["RedirectURI"].isNull());
+                  EXPECT_TRUE(payload["redirectType"].isNull());
+                  EXPECT_TRUE(payload["isHttpToHttpsRedirect"].isNull());
+                  EXPECT_TRUE(payload["redirectId"].isNull());
+                  EXPECT_EQ_JSON(payload["contentType"], String, "text/html");
+
+                } else if (nameString == "Load 3: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_redirect_temporary);
+                  state = State(S_NetworkMarkerPayload_redirect_temporary + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 3);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_EQ_JSON(payload["RedirectURI"], String,
+                                 "http://example.com/");
+                  EXPECT_EQ_JSON(payload["redirectType"], String, "Temporary");
+                  EXPECT_EQ_JSON(payload["isHttpToHttpsRedirect"], Bool, false);
+                  EXPECT_EQ_JSON(payload["redirectId"], Int64, 103);
+                  EXPECT_TRUE(payload["contentType"].isNull());
+
+                } else if (nameString == "Load 4: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_redirect_permanent);
+                  state = State(S_NetworkMarkerPayload_redirect_permanent + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 4);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_EQ_JSON(payload["RedirectURI"], String,
+                                 "http://example.com/");
+                  EXPECT_EQ_JSON(payload["redirectType"], String, "Permanent");
+                  EXPECT_EQ_JSON(payload["isHttpToHttpsRedirect"], Bool, false);
+                  EXPECT_EQ_JSON(payload["redirectId"], Int64, 104);
+                  EXPECT_TRUE(payload["contentType"].isNull());
+
+                } else if (nameString == "Load 5: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_redirect_internal);
+                  state = State(S_NetworkMarkerPayload_redirect_internal + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 5);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_EQ_JSON(payload["RedirectURI"], String,
+                                 "http://example.com/");
+                  EXPECT_EQ_JSON(payload["redirectType"], String, "Internal");
+                  EXPECT_EQ_JSON(payload["isHttpToHttpsRedirect"], Bool, false);
+                  EXPECT_EQ_JSON(payload["redirectId"], Int64, 105);
+                  EXPECT_TRUE(payload["contentType"].isNull());
+
+                } else if (nameString == "Load 6: http://mozilla.org/") {
+                  EXPECT_EQ(state,
+                            S_NetworkMarkerPayload_redirect_internal_sts);
+                  state =
+                      State(S_NetworkMarkerPayload_redirect_internal_sts + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 6);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_TRUE(payload["isPrivateBrowsing"].isNull());
+                  EXPECT_EQ_JSON(payload["RedirectURI"], String,
+                                 "http://example.com/");
+                  EXPECT_EQ_JSON(payload["redirectType"], String, "Internal");
+                  EXPECT_EQ_JSON(payload["isHttpToHttpsRedirect"], Bool, true);
+                  EXPECT_EQ_JSON(payload["redirectId"], Int64, 106);
+                  EXPECT_TRUE(payload["contentType"].isNull());
+
+                } else if (nameString == "Load 7: http://mozilla.org/") {
+                  EXPECT_EQ(state, S_NetworkMarkerPayload_private_browsing);
+                  state = State(S_NetworkMarkerPayload_private_browsing + 1);
+                  EXPECT_EQ(typeString, "Network");
+                  EXPECT_EQ_JSON(payload["startTime"], Double, ts1Double);
+                  EXPECT_EQ_JSON(payload["endTime"], Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["id"], Int64, 7);
+                  EXPECT_EQ_JSON(payload["URI"], String, "http://mozilla.org/");
+                  EXPECT_EQ_JSON(payload["requestMethod"], String, "GET");
+                  EXPECT_EQ_JSON(payload["pri"], Int64, 34);
+                  EXPECT_EQ_JSON(payload["count"], Int64, 56);
+                  EXPECT_EQ_JSON(payload["cache"], String, "Unresolved");
+                  EXPECT_EQ_JSON(payload["isPrivateBrowsing"], Bool, true);
+                  EXPECT_TRUE(payload["RedirectURI"].isNull());
+                  EXPECT_TRUE(payload["redirectType"].isNull());
+                  EXPECT_TRUE(payload["isHttpToHttpsRedirect"].isNull());
+                  EXPECT_TRUE(payload["redirectId"].isNull());
+                  EXPECT_TRUE(payload["contentType"].isNull());
+                } else if (nameString == "Text in main thread with stack") {
+                  EXPECT_EQ(state, S_TextWithStack);
+                  state = State(S_TextWithStack + 1);
+                  EXPECT_EQ(typeString, "Text");
+                  EXPECT_FALSE(payload["stack"].isNull());
+                  EXPECT_TIMING_INTERVAL_AT(ts1Double, ts2Double);
+                  EXPECT_EQ_JSON(payload["name"], String, "");
+
+                } else if (nameString == "Text from main thread with stack") {
+                  EXPECT_EQ(state, S_TextToMTWithStack);
+                  state = State(S_TextToMTWithStack + 1);
+                  EXPECT_EQ(typeString, "Text");
+                  EXPECT_FALSE(payload["stack"].isNull());
+                  EXPECT_EQ_JSON(payload["name"], String, "");
+
+                } else if (nameString ==
+                           "Text in registered thread with stack") {
+                  ADD_FAILURE()
+                      << "Unexpected 'Text in registered thread with stack'";
+
+                } else if (nameString ==
+                           "Text from registered thread with stack") {
+                  EXPECT_EQ(state, S_RegThread_TextToMTWithStack);
+                  state = State(S_RegThread_TextToMTWithStack + 1);
+                  EXPECT_EQ(typeString, "Text");
+                  EXPECT_FALSE(payload["stack"].isNull());
+                  EXPECT_EQ_JSON(payload["name"], String, "");
+
+                } else if (nameString ==
+                           "Text in unregistered thread with stack") {
+                  ADD_FAILURE()
+                      << "Unexpected 'Text in unregistered thread with stack'";
+
+                } else if (nameString ==
+                           "Text from unregistered thread with stack") {
+                  EXPECT_EQ(state, S_UnregThread_TextToMTWithStack);
+                  state = State(S_UnregThread_TextToMTWithStack + 1);
+                  EXPECT_EQ(typeString, "Text");
+                  EXPECT_TRUE(payload["stack"].isNull());
+                  EXPECT_EQ_JSON(payload["name"], String, "");
+                }
+              }  // marker with payload
+            }    // for (marker : data)
+          }      // markers.data
+        }        // markers
+      }          // thread0
+    }            // threads
+    // We should have read all expected markers.
+    EXPECT_EQ(state, S_LAST);
+
+    {
+      GET_JSON(meta, root["meta"], Object);
+
+      {
+        GET_JSON(markerSchema, meta["markerSchema"], Array);
+
+        std::set<std::string> testedSchemaNames;
+
+        for (const Json::Value& schema : markerSchema) {
+          GET_JSON(name, schema["name"], String);
+          const std::string nameString = name.asString();
+
+          GET_JSON(display, schema["display"], Array);
+
+          GET_JSON(data, schema["data"], Array);
+
+          EXPECT_TRUE(
+              testedSchemaNames
+                  .insert(std::string(nameString.data(), nameString.size()))
+                  .second)
+              << "Each schema name should be unique (inserted once in the set)";
+
+          if (nameString == "Text") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 1u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "name");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Details");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "string");
+
+          } else if (nameString == "NoPayloadUserData") {
+            // TODO: Remove this when bug 1646714 lands.
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 0u);
+
+          } else if (nameString == "FileIO") {
+            // These are defined in ProfilerIOInterposeObserver.cpp
+
+          } else if (nameString == "tracing") {
+            EXPECT_EQ(display.size(), 3u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+            EXPECT_EQ(display[2u].asString(), "timeline-overview");
+
+            ASSERT_EQ(data.size(), 1u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "category");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Type");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "string");
+
+          } else if (nameString == "BHR-detected hang") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 0u);
+
+          } else if (nameString == "MainThreadLongTask") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 1u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "category");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Type");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "string");
+
+          } else if (nameString == "Log") {
+            EXPECT_EQ(display.size(), 1u);
+            EXPECT_EQ(display[0u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 2u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "module");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Module");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "string");
+
+            ASSERT_TRUE(data[1u].isObject());
+            EXPECT_EQ_JSON(data[1u]["key"], String, "name");
+            EXPECT_EQ_JSON(data[1u]["label"], String, "Name");
+            EXPECT_EQ_JSON(data[1u]["format"], String, "string");
+
+          } else if (nameString == "MediaSample") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 3u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "sampleStartTimeUs");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Sample start time");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "microseconds");
+
+            ASSERT_TRUE(data[1u].isObject());
+            EXPECT_EQ_JSON(data[1u]["key"], String, "sampleEndTimeUs");
+            EXPECT_EQ_JSON(data[1u]["label"], String, "Sample end time");
+            EXPECT_EQ_JSON(data[1u]["format"], String, "microseconds");
+
+            ASSERT_TRUE(data[2u].isObject());
+            EXPECT_EQ_JSON(data[2u]["key"], String, "queueLength");
+            EXPECT_EQ_JSON(data[2u]["label"], String, "Queue length");
+            EXPECT_EQ_JSON(data[2u]["format"], String, "integer");
+
+          } else if (nameString == "VideoFallingBehind") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 2u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "videoFrameStartTimeUs");
+            EXPECT_EQ_JSON(data[0u]["label"], String, "Video frame start time");
+            EXPECT_EQ_JSON(data[0u]["format"], String, "microseconds");
+
+            ASSERT_TRUE(data[1u].isObject());
+            EXPECT_EQ_JSON(data[1u]["key"], String, "mediaCurrentTimeUs");
+            EXPECT_EQ_JSON(data[1u]["label"], String, "Media current time");
+            EXPECT_EQ_JSON(data[1u]["format"], String, "microseconds");
+
+          } else if (nameString == "Budget") {
+            EXPECT_EQ(display.size(), 2u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+
+            ASSERT_EQ(data.size(), 0u);
+
+          } else if (nameString == "markers-gtest") {
+            EXPECT_EQ(display.size(), 7u);
+            EXPECT_EQ(display[0u].asString(), "marker-chart");
+            EXPECT_EQ(display[1u].asString(), "marker-table");
+            EXPECT_EQ(display[2u].asString(), "timeline-overview");
+            EXPECT_EQ(display[3u].asString(), "timeline-memory");
+            EXPECT_EQ(display[4u].asString(), "timeline-ipc");
+            EXPECT_EQ(display[5u].asString(), "timeline-fileio");
+            EXPECT_EQ(display[6u].asString(), "stack-chart");
+
+            EXPECT_EQ_JSON(schema["chartLabel"], String, "chart label");
+            EXPECT_EQ_JSON(schema["tooltipLabel"], String, "tooltip label");
+            EXPECT_EQ_JSON(schema["tableLabel"], String, "table label");
+
+            ASSERT_EQ(data.size(), 14u);
+
+            ASSERT_TRUE(data[0u].isObject());
+            EXPECT_EQ_JSON(data[0u]["key"], String, "key with url");
+            EXPECT_TRUE(data[0u]["label"].isNull());
+            EXPECT_EQ_JSON(data[0u]["format"], String, "url");
+            EXPECT_TRUE(data[0u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[1u].isObject());
+            EXPECT_EQ_JSON(data[1u]["key"], String, "key with label filePath");
+            EXPECT_EQ_JSON(data[1u]["label"], String, "label filePath");
+            EXPECT_EQ_JSON(data[1u]["format"], String, "file-path");
+            EXPECT_TRUE(data[1u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[2u].isObject());
+            EXPECT_EQ_JSON(data[2u]["key"], String,
+                           "key with string not-searchable");
+            EXPECT_TRUE(data[2u]["label"].isNull());
+            EXPECT_EQ_JSON(data[2u]["format"], String, "string");
+            EXPECT_EQ_JSON(data[2u]["searchable"], Bool, false);
+
+            ASSERT_TRUE(data[3u].isObject());
+            EXPECT_EQ_JSON(data[3u]["key"], String,
+                           "key with label duration searchable");
+            EXPECT_TRUE(data[3u]["label duration"].isNull());
+            EXPECT_EQ_JSON(data[3u]["format"], String, "duration");
+            EXPECT_EQ_JSON(data[3u]["searchable"], Bool, true);
+
+            ASSERT_TRUE(data[4u].isObject());
+            EXPECT_EQ_JSON(data[4u]["key"], String, "key with time");
+            EXPECT_TRUE(data[4u]["label"].isNull());
+            EXPECT_EQ_JSON(data[4u]["format"], String, "time");
+            EXPECT_TRUE(data[4u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[5u].isObject());
+            EXPECT_EQ_JSON(data[5u]["key"], String, "key with seconds");
+            EXPECT_TRUE(data[5u]["label"].isNull());
+            EXPECT_EQ_JSON(data[5u]["format"], String, "seconds");
+            EXPECT_TRUE(data[5u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[6u].isObject());
+            EXPECT_EQ_JSON(data[6u]["key"], String, "key with milliseconds");
+            EXPECT_TRUE(data[6u]["label"].isNull());
+            EXPECT_EQ_JSON(data[6u]["format"], String, "milliseconds");
+            EXPECT_TRUE(data[6u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[7u].isObject());
+            EXPECT_EQ_JSON(data[7u]["key"], String, "key with microseconds");
+            EXPECT_TRUE(data[7u]["label"].isNull());
+            EXPECT_EQ_JSON(data[7u]["format"], String, "microseconds");
+            EXPECT_TRUE(data[7u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[8u].isObject());
+            EXPECT_EQ_JSON(data[8u]["key"], String, "key with nanoseconds");
+            EXPECT_TRUE(data[8u]["label"].isNull());
+            EXPECT_EQ_JSON(data[8u]["format"], String, "nanoseconds");
+            EXPECT_TRUE(data[8u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[9u].isObject());
+            EXPECT_EQ_JSON(data[9u]["key"], String, "key with bytes");
+            EXPECT_TRUE(data[9u]["label"].isNull());
+            EXPECT_EQ_JSON(data[9u]["format"], String, "bytes");
+            EXPECT_TRUE(data[9u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[10u].isObject());
+            EXPECT_EQ_JSON(data[10u]["key"], String, "key with percentage");
+            EXPECT_TRUE(data[10u]["label"].isNull());
+            EXPECT_EQ_JSON(data[10u]["format"], String, "percentage");
+            EXPECT_TRUE(data[10u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[11u].isObject());
+            EXPECT_EQ_JSON(data[11u]["key"], String, "key with integer");
+            EXPECT_TRUE(data[11u]["label"].isNull());
+            EXPECT_EQ_JSON(data[11u]["format"], String, "integer");
+            EXPECT_TRUE(data[11u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[12u].isObject());
+            EXPECT_EQ_JSON(data[12u]["key"], String, "key with decimal");
+            EXPECT_TRUE(data[12u]["label"].isNull());
+            EXPECT_EQ_JSON(data[12u]["format"], String, "decimal");
+            EXPECT_TRUE(data[12u]["searchable"].isNull());
+
+            ASSERT_TRUE(data[13u].isObject());
+            EXPECT_EQ_JSON(data[13u]["label"], String, "static label");
+            EXPECT_EQ_JSON(data[13u]["value"], String, "static value");
+
+          } else if (nameString == "markers-gtest-special") {
+            EXPECT_EQ(display.size(), 0u);
+            ASSERT_EQ(data.size(), 0u);
+
+          } else if (nameString == "markers-gtest-unused") {
+            ADD_FAILURE() << "Schema for GtestUnusedMarker should not be here";
+
+          } else {
+            printf("FYI: Unknown marker schema '%s'\n", nameString.c_str());
+          }
+        }
+
+        // Check that we've got all expected schema.
+        EXPECT_TRUE(testedSchemaNames.find("Text") != testedSchemaNames.end());
+        EXPECT_TRUE(testedSchemaNames.find("tracing") !=
+                    testedSchemaNames.end());
+        EXPECT_TRUE(testedSchemaNames.find("MediaSample") !=
+                    testedSchemaNames.end());
+      }  // markerSchema
+    }    // meta
+  });
+
+  Maybe<ProfilerBufferInfo> info = profiler_get_buffer_info();
+  EXPECT_TRUE(info.isSome());
+  printf("Profiler buffer range: %llu .. %llu (%llu bytes)\n",
+         static_cast<unsigned long long>(info->mRangeStart),
+         static_cast<unsigned long long>(info->mRangeEnd),
+         // sizeof(ProfileBufferEntry) == 9
+         (static_cast<unsigned long long>(info->mRangeEnd) -
+          static_cast<unsigned long long>(info->mRangeStart)) *
+             9);
+  printf("Stats:         min(us) .. mean(us) .. max(us)  [count]\n");
+  printf("- Intervals:   %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mIntervalsUs.min, info->mIntervalsUs.sum / info->mIntervalsUs.n,
+         info->mIntervalsUs.max, info->mIntervalsUs.n);
+  printf("- Overheads:   %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mOverheadsUs.min, info->mOverheadsUs.sum / info->mOverheadsUs.n,
+         info->mOverheadsUs.max, info->mOverheadsUs.n);
+  printf("  - Locking:   %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mLockingsUs.min, info->mLockingsUs.sum / info->mLockingsUs.n,
+         info->mLockingsUs.max, info->mLockingsUs.n);
+  printf("  - Clearning: %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mCleaningsUs.min, info->mCleaningsUs.sum / info->mCleaningsUs.n,
+         info->mCleaningsUs.max, info->mCleaningsUs.n);
+  printf("  - Counters:  %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mCountersUs.min, info->mCountersUs.sum / info->mCountersUs.n,
+         info->mCountersUs.max, info->mCountersUs.n);
+  printf("  - Threads:   %7.1f .. %7.1f  .. %7.1f  [%u]\n",
+         info->mThreadsUs.min, info->mThreadsUs.sum / info->mThreadsUs.n,
+         info->mThreadsUs.max, info->mThreadsUs.n);
+
+  profiler_stop();
+
+  // Try to add markers while the profiler is stopped.
+  PROFILER_MARKER_UNTYPED("marker after profiler_stop", OTHER);
+
+  // Warning: this could be racy
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  // This last marker shouldn't get streamed.
+  SpliceableChunkedJSONWriter w2{FailureLatchInfallibleSource::Singleton()};
+  w2.Start();
+  EXPECT_TRUE(::profiler_stream_json_for_this_process(w2));
+  w2.End();
+  EXPECT_FALSE(w2.Failed());
+  UniquePtr<char[]> profile2 = w2.ChunkedWriteFunc().CopyData();
+  ASSERT_TRUE(!!profile2.get());
+  EXPECT_TRUE(
+      std::string_view(profile2.get()).find("marker after profiler_stop") ==
+      std::string_view::npos);
+
+  profiler_stop();
+}
+
+#  define COUNTER_NAME "TestCounter"
+#  define COUNTER_DESCRIPTION "Test of counters in profiles"
+#  define COUNTER_NAME2 "Counter2"
+#  define COUNTER_DESCRIPTION2 "Second Test of counters in profiles"
+
+PROFILER_DEFINE_COUNT_TOTAL(TestCounter, COUNTER_NAME, COUNTER_DESCRIPTION);
+PROFILER_DEFINE_COUNT_TOTAL(TestCounter2, COUNTER_NAME2, COUNTER_DESCRIPTION2);
+
+TEST(GeckoProfiler, Counters)
+{
+  uint32_t features = 0;
+  const char* filters[] = {"GeckoMain"};
+
+  // We will record some counter values, and check that they're present (and no
+  // other) when expected.
+
+  struct NumberAndCount {
+    uint64_t mNumber;
+    int64_t mCount;
+  };
+
+  int64_t testCounters[] = {10, 7, -17};
+  NumberAndCount expectedTestCounters[] = {{1u, 10}, {0u, 0}, {1u, 7},
+                                           {0u, 0},  {0u, 0}, {1u, -17},
+                                           {0u, 0},  {0u, 0}};
+  constexpr size_t expectedTestCountersCount =
+      MOZ_ARRAY_LENGTH(expectedTestCounters);
+
+  bool expectCounter2 = false;
+  int64_t testCounters2[] = {10};
+  NumberAndCount expectedTestCounters2[] = {{1u, 10}, {0u, 0}};
+  constexpr size_t expectedTestCounters2Count =
+      MOZ_ARRAY_LENGTH(expectedTestCounters2);
+
+  auto checkCountersInJSON = [&](const Json::Value& aRoot) {
+    size_t nextExpectedTestCounter = 0u;
+    size_t nextExpectedTestCounter2 = 0u;
+
+    GET_JSON(counters, aRoot["counters"], Array);
+    for (const Json::Value& counter : counters) {
+      ASSERT_TRUE(counter.isObject());
+      GET_JSON_VALUE(name, counter["name"], String);
+      if (name == "TestCounter") {
+        EXPECT_EQ_JSON(counter["category"], String, COUNTER_NAME);
+        EXPECT_EQ_JSON(counter["description"], String, COUNTER_DESCRIPTION);
+        GET_JSON(sampleGroups, counter["sample_groups"], Array);
+        for (const Json::Value& sampleGroup : sampleGroups) {
+          ASSERT_TRUE(sampleGroup.isObject());
+          EXPECT_EQ_JSON(sampleGroup["id"], UInt, 0u);
+
+          GET_JSON(samples, sampleGroup["samples"], Object);
+          GET_JSON(samplesSchema, samples["schema"], Object);
+          EXPECT_GE(samplesSchema.size(), 3u);
+          GET_JSON_VALUE(samplesNumber, samplesSchema["number"], UInt);
+          GET_JSON_VALUE(samplesCount, samplesSchema["count"], UInt);
+          GET_JSON(samplesData, samples["data"], Array);
+          for (const Json::Value& sample : samplesData) {
+            ASSERT_TRUE(sample.isArray());
+            ASSERT_LT(nextExpectedTestCounter, expectedTestCountersCount);
+            EXPECT_EQ_JSON(
+                sample[samplesNumber], UInt64,
+                expectedTestCounters[nextExpectedTestCounter].mNumber);
+            EXPECT_EQ_JSON(
+                sample[samplesCount], Int64,
+                expectedTestCounters[nextExpectedTestCounter].mCount);
+            ++nextExpectedTestCounter;
+          }
+        }
+      } else if (name == "TestCounter2") {
+        EXPECT_TRUE(expectCounter2);
+
+        EXPECT_EQ_JSON(counter["category"], String, COUNTER_NAME2);
+        EXPECT_EQ_JSON(counter["description"], String, COUNTER_DESCRIPTION2);
+        GET_JSON(sampleGroups, counter["sample_groups"], Array);
+        for (const Json::Value& sampleGroup : sampleGroups) {
+          ASSERT_TRUE(sampleGroup.isObject());
+          EXPECT_EQ_JSON(sampleGroup["id"], UInt, 0u);
+
+          GET_JSON(samples, sampleGroup["samples"], Object);
+          GET_JSON(samplesSchema, samples["schema"], Object);
+          EXPECT_GE(samplesSchema.size(), 3u);
+          GET_JSON_VALUE(samplesNumber, samplesSchema["number"], UInt);
+          GET_JSON_VALUE(samplesCount, samplesSchema["count"], UInt);
+          GET_JSON(samplesData, samples["data"], Array);
+          for (const Json::Value& sample : samplesData) {
+            ASSERT_TRUE(sample.isArray());
+            ASSERT_LT(nextExpectedTestCounter2, expectedTestCounters2Count);
+            EXPECT_EQ_JSON(
+                sample[samplesNumber], UInt64,
+                expectedTestCounters2[nextExpectedTestCounter2].mNumber);
+            EXPECT_EQ_JSON(
+                sample[samplesCount], Int64,
+                expectedTestCounters2[nextExpectedTestCounter2].mCount);
+            ++nextExpectedTestCounter2;
+          }
+        }
+      }
+    }
+
+    EXPECT_EQ(nextExpectedTestCounter, expectedTestCountersCount);
+    if (expectCounter2) {
+      EXPECT_EQ(nextExpectedTestCounter2, expectedTestCounters2Count);
+    }
+  };
+
+  // Inactive -> Active
+  profiler_ensure_started(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                          features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  // Output all "TestCounter"s, with increasing delays (to test different
+  // number of counter samplings).
+  int samplingWaits = 2;
+  for (int64_t counter : testCounters) {
+    AUTO_PROFILER_COUNT_TOTAL(TestCounter, counter);
+    for (int i = 0; i < samplingWaits; ++i) {
+      ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+    }
+    ++samplingWaits;
+  }
+
+  // Verify we got "TestCounter" in the output, but not "TestCounter2" yet.
+  UniquePtr<char[]> profile = profiler_get_profile();
+  JSONOutputCheck(profile.get(), checkCountersInJSON);
+
+  // Now introduce TestCounter2.
+  expectCounter2 = true;
+  for (int64_t counter2 : testCounters2) {
+    AUTO_PROFILER_COUNT_TOTAL(TestCounter2, counter2);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  }
+
+  // Verify we got both "TestCounter" and "TestCounter2" in the output.
+  profile = profiler_get_profile();
+  JSONOutputCheck(profile.get(), checkCountersInJSON);
+
+  profiler_stop();
+}
+
+TEST(GeckoProfiler, Time)
+{
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  double t1 = profiler_time();
+  double t2 = profiler_time();
+  ASSERT_TRUE(t1 <= t2);
+
+  // profiler_start() restarts the timer used by profiler_time().
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  double t3 = profiler_time();
+  double t4 = profiler_time();
+  ASSERT_TRUE(t3 <= t4);
+
+  profiler_stop();
+
+  double t5 = profiler_time();
+  double t6 = profiler_time();
+  ASSERT_TRUE(t4 <= t5 && t1 <= t6);
+}
+
+TEST(GeckoProfiler, GetProfile)
+{
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  ASSERT_TRUE(!profiler_get_profile());
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  mozilla::Maybe<uint32_t> activeFeatures = profiler_features_if_active();
+  ASSERT_TRUE(activeFeatures.isSome());
+  // Not all platforms support stack-walking.
+  const bool hasStackWalk = ProfilerFeature::HasStackWalk(*activeFeatures);
+
+  UniquePtr<char[]> profile = profiler_get_profile();
+  JSONOutputCheck(profile.get(), [&](const Json::Value& aRoot) {
+    GET_JSON(meta, aRoot["meta"], Object);
+    {
+      GET_JSON(configuration, meta["configuration"], Object);
+      {
+        GET_JSON(features, configuration["features"], Array);
+        {
+          EXPECT_EQ(features.size(), (hasStackWalk ? 1u : 0u));
+          if (hasStackWalk) {
+            EXPECT_JSON_ARRAY_CONTAINS(features, String, "stackwalk");
+          }
+        }
+        GET_JSON(threads, configuration["threads"], Array);
+        {
+          EXPECT_EQ(threads.size(), 1u);
+          EXPECT_JSON_ARRAY_CONTAINS(threads, String, "GeckoMain");
+        }
+      }
+    }
+  });
+
+  profiler_stop();
+
+  ASSERT_TRUE(!profiler_get_profile());
+}
+
+TEST(GeckoProfiler, StreamJSONForThisProcess)
+{
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  SpliceableChunkedJSONWriter w{FailureLatchInfallibleSource::Singleton()};
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Fallible());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(&w.ChunkedWriteFunc().SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(
+      &std::as_const(w.ChunkedWriteFunc()).SourceFailureLatch() ==
+      &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(!w.Fallible());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+  MOZ_RELEASE_ASSERT(&w.SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(&std::as_const(w).SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+
+  ASSERT_TRUE(!::profiler_stream_json_for_this_process(w));
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  w.Start();
+  ASSERT_TRUE(::profiler_stream_json_for_this_process(w));
+  w.End();
+
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+
+  UniquePtr<char[]> profile = w.ChunkedWriteFunc().CopyData();
+
+  JSONOutputCheck(profile.get(), [](const Json::Value&) {});
+
+  profiler_stop();
+
+  ASSERT_TRUE(!::profiler_stream_json_for_this_process(w));
+}
+
+// Internal version of profiler_stream_json_for_this_process, which allows being
+// called from a non-main thread of the parent process, at the risk of getting
+// an incomplete profile.
+bool do_profiler_stream_json_for_this_process(
+    SpliceableJSONWriter& aWriter, double aSinceTime, bool aIsShuttingDown,
+    ProfilerCodeAddressService* aService,
+    mozilla::ProgressLogger aProgressLogger);
+
+TEST(GeckoProfiler, StreamJSONForThisProcessThreaded)
+{
+  // Same as the previous test, but calling some things on background threads.
+  nsCOMPtr<nsIThread> thread;
+  nsresult rv = NS_NewNamedThread("GeckoProfGTest", getter_AddRefs(thread));
+  ASSERT_NS_SUCCEEDED(rv);
+
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  SpliceableChunkedJSONWriter w{FailureLatchInfallibleSource::Singleton()};
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Fallible());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(&w.ChunkedWriteFunc().SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(
+      &std::as_const(w.ChunkedWriteFunc()).SourceFailureLatch() ==
+      &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(!w.Fallible());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+  MOZ_RELEASE_ASSERT(&w.SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+  MOZ_RELEASE_ASSERT(&std::as_const(w).SourceFailureLatch() ==
+                     &mozilla::FailureLatchInfallibleSource::Singleton());
+
+  ASSERT_TRUE(!::profiler_stream_json_for_this_process(w));
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+
+  // Start the profiler on the main thread.
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  // Call profiler_stream_json_for_this_process on a background thread.
+  thread->Dispatch(
+      NS_NewRunnableFunction(
+          "GeckoProfiler_StreamJSONForThisProcessThreaded_Test::TestBody",
+          [&]() {
+            w.Start();
+            ASSERT_TRUE(::do_profiler_stream_json_for_this_process(
+                w, /* double aSinceTime */ 0.0,
+                /* bool aIsShuttingDown */ false,
+                /* ProfilerCodeAddressService* aService */ nullptr,
+                mozilla::ProgressLogger{}));
+            w.End();
+          }),
+      NS_DISPATCH_SYNC);
+
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().Failed());
+  MOZ_RELEASE_ASSERT(!w.ChunkedWriteFunc().GetFailure());
+  MOZ_RELEASE_ASSERT(!w.Failed());
+  MOZ_RELEASE_ASSERT(!w.GetFailure());
+
+  UniquePtr<char[]> profile = w.ChunkedWriteFunc().CopyData();
+
+  JSONOutputCheck(profile.get(), [](const Json::Value&) {});
+
+  // Stop the profiler and call profiler_stream_json_for_this_process on a
+  // background thread.
+  thread->Dispatch(
+      NS_NewRunnableFunction(
+          "GeckoProfiler_StreamJSONForThisProcessThreaded_Test::TestBody",
+          [&]() {
+            profiler_stop();
+            ASSERT_TRUE(!::do_profiler_stream_json_for_this_process(
+                w, /* double aSinceTime */ 0.0,
+                /* bool aIsShuttingDown */ false,
+                /* ProfilerCodeAddressService* aService */ nullptr,
+                mozilla::ProgressLogger{}));
+          }),
+      NS_DISPATCH_SYNC);
+  thread->Shutdown();
+
+  // Call profiler_stream_json_for_this_process on the main thread.
+  ASSERT_TRUE(!::profiler_stream_json_for_this_process(w));
+}
+
+TEST(GeckoProfiler, ProfilingStack)
+{
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+
+  AUTO_PROFILER_LABEL("A::B", OTHER);
+
+  UniqueFreePtr<char> dynamic(strdup("dynamic"));
+  {
+    AUTO_PROFILER_LABEL_DYNAMIC_CSTR("A::C", JS, dynamic.get());
+    AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("A::C2", JS,
+                                          nsDependentCString(dynamic.get()));
+    AUTO_PROFILER_LABEL_DYNAMIC_LOSSY_NSSTRING(
+        "A::C3", JS, NS_ConvertUTF8toUTF16(dynamic.get()));
+
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+    ASSERT_TRUE(profiler_get_backtrace());
+  }
+
+  AutoProfilerLabel label1("A", nullptr, JS::ProfilingCategoryPair::DOM);
+  AutoProfilerLabel label2("A", dynamic.get(),
+                           JS::ProfilingCategoryPair::NETWORK);
+  ASSERT_TRUE(profiler_get_backtrace());
+
+  profiler_stop();
+
+  ASSERT_TRUE(!profiler_get_profile());
+}
+
+TEST(GeckoProfiler, Bug1355807)
+{
+  uint32_t features = ProfilerFeature::JS;
+  const char* manyThreadsFilter[] = {""};
+  const char* fewThreadsFilter[] = {"GeckoMain"};
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 manyThreadsFilter, MOZ_ARRAY_LENGTH(manyThreadsFilter), 0);
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 fewThreadsFilter, MOZ_ARRAY_LENGTH(fewThreadsFilter), 0);
+
+  // In bug 1355807 this caused an assertion failure in StopJSSampling().
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 fewThreadsFilter, MOZ_ARRAY_LENGTH(fewThreadsFilter), 0);
+
+  profiler_stop();
+}
+
+class GTestStackCollector final : public ProfilerStackCollector {
+ public:
+  GTestStackCollector() : mSetIsMainThread(0), mFrames(0) {}
+
+  virtual void SetIsMainThread() { mSetIsMainThread++; }
+
+  virtual void CollectNativeLeafAddr(void* aAddr) { mFrames++; }
+  virtual void CollectJitReturnAddr(void* aAddr) { mFrames++; }
+  virtual void CollectWasmFrame(const char* aLabel) { mFrames++; }
+  virtual void CollectProfilingStackFrame(
+      const js::ProfilingStackFrame& aFrame) {
+    mFrames++;
+  }
+
+  int mSetIsMainThread;
+  int mFrames;
+};
+
+void DoSuspendAndSample(ProfilerThreadId aTidToSample,
+                        nsIThread* aSamplingThread) {
+  aSamplingThread->Dispatch(
+      NS_NewRunnableFunction(
+          "GeckoProfiler_SuspendAndSample_Test::TestBody",
+          [&]() {
+            uint32_t features = ProfilerFeature::CPUUtilization;
+            GTestStackCollector collector;
+            profiler_suspend_and_sample_thread(aTidToSample, features,
+                                               collector,
+                                               /* sampleNative = */ true);
+
+            ASSERT_TRUE(collector.mSetIsMainThread ==
+                        (aTidToSample == profiler_main_thread_id()));
+            ASSERT_TRUE(collector.mFrames > 0);
+          }),
+      NS_DISPATCH_SYNC);
+}
+
+TEST(GeckoProfiler, SuspendAndSample)
+{
+  nsCOMPtr<nsIThread> thread;
+  nsresult rv = NS_NewNamedThread("GeckoProfGTest", getter_AddRefs(thread));
+  ASSERT_NS_SUCCEEDED(rv);
+
+  ProfilerThreadId tid = profiler_current_thread_id();
+
+  ASSERT_TRUE(!profiler_is_active());
+
+  // Suspend and sample while the profiler is inactive.
+  DoSuspendAndSample(tid, thread);
+
+  DoSuspendAndSample(ProfilerThreadId{}, thread);
+
+  uint32_t features = ProfilerFeature::JS;
+  const char* filters[] = {"GeckoMain", "Compositor"};
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  ASSERT_TRUE(profiler_is_active());
+
+  // Suspend and sample while the profiler is active.
+  DoSuspendAndSample(tid, thread);
+
+  DoSuspendAndSample(ProfilerThreadId{}, thread);
+
+  profiler_stop();
+
+  ASSERT_TRUE(!profiler_is_active());
+}
+
+TEST(GeckoProfiler, PostSamplingCallback)
+{
+  const char* filters[] = {"GeckoMain"};
+
+  ASSERT_TRUE(!profiler_is_active());
+  ASSERT_TRUE(!profiler_callback_after_sampling(
+      [&](SamplingState) { ASSERT_TRUE(false); }));
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                 ProfilerFeature::StackWalk, filters, MOZ_ARRAY_LENGTH(filters),
+                 0);
+  {
+    // Stack sampling -> This label should appear at least once.
+    AUTO_PROFILER_LABEL("PostSamplingCallback completed", OTHER);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  }
+  UniquePtr<char[]> profileCompleted = profiler_get_profile();
+  JSONOutputCheck(profileCompleted.get(), [](const Json::Value& aRoot) {
+    GET_JSON(threads, aRoot["threads"], Array);
+    {
+      GET_JSON(thread0, threads[0], Object);
+      {
+        EXPECT_JSON_ARRAY_CONTAINS(thread0["stringTable"], String,
+                                   "PostSamplingCallback completed");
+      }
+    }
+  });
+
+  profiler_pause();
+  {
+    // Paused -> This label should not appear.
+    AUTO_PROFILER_LABEL("PostSamplingCallback paused", OTHER);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingPaused);
+  }
+  UniquePtr<char[]> profilePaused = profiler_get_profile();
+  JSONOutputCheck(profilePaused.get(), [](const Json::Value& aRoot) {});
+  // This string shouldn't appear *anywhere* in the profile.
+  ASSERT_FALSE(strstr(profilePaused.get(), "PostSamplingCallback paused"));
+
+  profiler_resume();
+  {
+    // Stack sampling -> This label should appear at least once.
+    AUTO_PROFILER_LABEL("PostSamplingCallback resumed", OTHER);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  }
+  UniquePtr<char[]> profileResumed = profiler_get_profile();
+  JSONOutputCheck(profileResumed.get(), [](const Json::Value& aRoot) {
+    GET_JSON(threads, aRoot["threads"], Array);
+    {
+      GET_JSON(thread0, threads[0], Object);
+      {
+        EXPECT_JSON_ARRAY_CONTAINS(thread0["stringTable"], String,
+                                   "PostSamplingCallback resumed");
+      }
+    }
+  });
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                 ProfilerFeature::StackWalk | ProfilerFeature::NoStackSampling,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+  {
+    // No stack sampling -> This label should not appear.
+    AUTO_PROFILER_LABEL("PostSamplingCallback completed (no stacks)", OTHER);
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::NoStackSamplingCompleted);
+  }
+  UniquePtr<char[]> profileNoStacks = profiler_get_profile();
+  JSONOutputCheck(profileNoStacks.get(), [](const Json::Value& aRoot) {});
+  // This string shouldn't appear *anywhere* in the profile.
+  ASSERT_FALSE(strstr(profileNoStacks.get(),
+                      "PostSamplingCallback completed (no stacks)"));
+
+  // Note: There is no non-racy way to test for SamplingState::JustStopped, as
+  // it would require coordination between `profiler_stop()` and another thread
+  // doing `profiler_callback_after_sampling()` at just the right moment.
+
+  profiler_stop();
+  ASSERT_TRUE(!profiler_is_active());
+  ASSERT_TRUE(!profiler_callback_after_sampling(
+      [&](SamplingState) { ASSERT_TRUE(false); }));
+}
+
+TEST(GeckoProfiler, ProfilingStateCallback)
+{
+  const char* filters[] = {"GeckoMain"};
+
+  ASSERT_TRUE(!profiler_is_active());
+
+  struct ProfilingStateAndId {
+    ProfilingState mProfilingState;
+    int mId;
+  };
+  DataMutex<Vector<ProfilingStateAndId>> states{"Profiling states"};
+  auto CreateCallback = [&states](int id) {
+    return [id, &states](ProfilingState aProfilingState) {
+      auto lockedStates = states.Lock();
+      ASSERT_TRUE(
+          lockedStates->append(ProfilingStateAndId{aProfilingState, id}));
+    };
+  };
+  auto CheckStatesIsEmpty = [&states]() {
+    auto lockedStates = states.Lock();
+    EXPECT_TRUE(lockedStates->empty());
+  };
+  auto CheckStatesOnlyContains = [&states](ProfilingState aProfilingState,
+                                           int aId) {
+    auto lockedStates = states.Lock();
+    EXPECT_EQ(lockedStates->length(), 1u);
+    if (lockedStates->length() >= 1u) {
+      EXPECT_EQ((*lockedStates)[0].mProfilingState, aProfilingState);
+      EXPECT_EQ((*lockedStates)[0].mId, aId);
+    }
+    lockedStates->clear();
+  };
+
+  profiler_add_state_change_callback(AllProfilingStates(), CreateCallback(1),
+                                     1);
+  // This is in case of error, and it also exercises the (allowed) removal of
+  // unknown callback ids.
+  auto cleanup1 = mozilla::MakeScopeExit(
+      []() { profiler_remove_state_change_callback(1); });
+  CheckStatesIsEmpty();
+
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                 ProfilerFeature::StackWalk, filters, MOZ_ARRAY_LENGTH(filters),
+                 0);
+
+  CheckStatesOnlyContains(ProfilingState::Started, 1);
+
+  profiler_add_state_change_callback(AllProfilingStates(), CreateCallback(2),
+                                     2);
+  // This is in case of error, and it also exercises the (allowed) removal of
+  // unknown callback ids.
+  auto cleanup2 = mozilla::MakeScopeExit(
+      []() { profiler_remove_state_change_callback(2); });
+  CheckStatesOnlyContains(ProfilingState::AlreadyActive, 2);
+
+  profiler_remove_state_change_callback(2);
+  CheckStatesOnlyContains(ProfilingState::RemovingCallback, 2);
+  // Note: The actual removal is effectively tested below, by not seeing any
+  // more invocations of the 2nd callback.
+
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  UniquePtr<char[]> profileCompleted = profiler_get_profile();
+  CheckStatesOnlyContains(ProfilingState::GeneratingProfile, 1);
+  JSONOutputCheck(profileCompleted.get(), [](const Json::Value& aRoot) {});
+
+  profiler_pause();
+  CheckStatesOnlyContains(ProfilingState::Pausing, 1);
+  UniquePtr<char[]> profilePaused = profiler_get_profile();
+  CheckStatesOnlyContains(ProfilingState::GeneratingProfile, 1);
+  JSONOutputCheck(profilePaused.get(), [](const Json::Value& aRoot) {});
+
+  profiler_resume();
+  CheckStatesOnlyContains(ProfilingState::Resumed, 1);
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  UniquePtr<char[]> profileResumed = profiler_get_profile();
+  CheckStatesOnlyContains(ProfilingState::GeneratingProfile, 1);
+  JSONOutputCheck(profileResumed.get(), [](const Json::Value& aRoot) {});
+
+  // This effectively stops the profiler before restarting it, but
+  // ProfilingState::Stopping is not notified. See `profiler_start` for details.
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                 ProfilerFeature::StackWalk | ProfilerFeature::NoStackSampling,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+  CheckStatesOnlyContains(ProfilingState::Started, 1);
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::NoStackSamplingCompleted);
+  UniquePtr<char[]> profileNoStacks = profiler_get_profile();
+  CheckStatesOnlyContains(ProfilingState::GeneratingProfile, 1);
+  JSONOutputCheck(profileNoStacks.get(), [](const Json::Value& aRoot) {});
+
+  profiler_stop();
+  CheckStatesOnlyContains(ProfilingState::Stopping, 1);
+  ASSERT_TRUE(!profiler_is_active());
+
+  profiler_remove_state_change_callback(1);
+  CheckStatesOnlyContains(ProfilingState::RemovingCallback, 1);
+
+  // Note: ProfilingState::ShuttingDown cannot be tested here, and the profiler
+  // can only be shut down once per process.
+}
+
+TEST(GeckoProfiler, BaseProfilerHandOff)
+{
+  const char* filters[] = {"GeckoMain"};
+
+  ASSERT_TRUE(!baseprofiler::profiler_is_active());
+  ASSERT_TRUE(!profiler_is_active());
+
+  BASE_PROFILER_MARKER_UNTYPED("Base marker before base profiler", OTHER, {});
+  PROFILER_MARKER_UNTYPED("Gecko marker before base profiler", OTHER, {});
+
+  // Start the Base Profiler.
+  baseprofiler::profiler_start(
+      PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+      ProfilerFeature::StackWalk, filters, MOZ_ARRAY_LENGTH(filters));
+
+  ASSERT_TRUE(baseprofiler::profiler_is_active());
+  ASSERT_TRUE(!profiler_is_active());
+
+  // Add at least a marker, which should go straight into the buffer.
+  Maybe<baseprofiler::ProfilerBufferInfo> info0 =
+      baseprofiler::profiler_get_buffer_info();
+  BASE_PROFILER_MARKER_UNTYPED("Base marker during base profiler", OTHER, {});
+  Maybe<baseprofiler::ProfilerBufferInfo> info1 =
+      baseprofiler::profiler_get_buffer_info();
+  ASSERT_GT(info1->mRangeEnd, info0->mRangeEnd);
+
+  PROFILER_MARKER_UNTYPED("Gecko marker during base profiler", OTHER, {});
+
+  // Start the Gecko Profiler, which should grab the Base Profiler profile and
+  // stop it.
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                 ProfilerFeature::StackWalk, filters, MOZ_ARRAY_LENGTH(filters),
+                 0);
+
+  ASSERT_TRUE(!baseprofiler::profiler_is_active());
+  ASSERT_TRUE(profiler_is_active());
+
+  BASE_PROFILER_MARKER_UNTYPED("Base marker during gecko profiler", OTHER, {});
+  PROFILER_MARKER_UNTYPED("Gecko marker during gecko profiler", OTHER, {});
+
+  // Write some Gecko Profiler samples.
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+
+  // Check that the Gecko Profiler profile contains at least the Base Profiler
+  // main thread samples.
+  UniquePtr<char[]> profile = profiler_get_profile();
+
+  profiler_stop();
+  ASSERT_TRUE(!profiler_is_active());
+
+  BASE_PROFILER_MARKER_UNTYPED("Base marker after gecko profiler", OTHER, {});
+  PROFILER_MARKER_UNTYPED("Gecko marker after gecko profiler", OTHER, {});
+
+  JSONOutputCheck(profile.get(), [](const Json::Value& aRoot) {
+    GET_JSON(threads, aRoot["threads"], Array);
+    {
+      bool found = false;
+      for (const Json::Value& thread : threads) {
+        ASSERT_TRUE(thread.isObject());
+        GET_JSON(name, thread["name"], String);
+        if (name.asString() == "GeckoMain") {
+          found = true;
+          EXPECT_JSON_ARRAY_EXCLUDES(thread["stringTable"], String,
+                                     "Base marker before base profiler");
+          EXPECT_JSON_ARRAY_EXCLUDES(thread["stringTable"], String,
+                                     "Gecko marker before base profiler");
+          EXPECT_JSON_ARRAY_CONTAINS(thread["stringTable"], String,
+                                     "Base marker during base profiler");
+          EXPECT_JSON_ARRAY_EXCLUDES(thread["stringTable"], String,
+                                     "Gecko marker during base profiler");
+          EXPECT_JSON_ARRAY_CONTAINS(thread["stringTable"], String,
+                                     "Base marker during gecko profiler");
+          EXPECT_JSON_ARRAY_CONTAINS(thread["stringTable"], String,
+                                     "Gecko marker during gecko profiler");
+          EXPECT_JSON_ARRAY_EXCLUDES(thread["stringTable"], String,
+                                     "Base marker after gecko profiler");
+          EXPECT_JSON_ARRAY_EXCLUDES(thread["stringTable"], String,
+                                     "Gecko marker after gecko profiler");
+          break;
+        }
+      }
+      EXPECT_TRUE(found);
+    }
+  });
+}
+
+static std::string_view GetFeatureName(uint32_t feature) {
+  switch (feature) {
+#  define FEATURE_NAME(n_, str_, Name_, desc_) \
+    case ProfilerFeature::Name_:               \
+      return str_;
+
+    PROFILER_FOR_EACH_FEATURE(FEATURE_NAME)
+
+#  undef FEATURE_NAME
+
+    default:
+      return "?";
+  }
+}
+
+TEST(GeckoProfiler, FeatureCombinations)
+{
+  const char* filters[] = {"*"};
+
+  // List of features to test. Every combination of up to 3 of them will be
+  // tested, so be careful not to add too many to keep the test run at a
+  // reasonable time.
+  uint32_t featureList[] = {ProfilerFeature::JS,
+                            ProfilerFeature::Screenshots,
+                            ProfilerFeature::StackWalk,
+                            ProfilerFeature::NoStackSampling,
+                            ProfilerFeature::NativeAllocations,
+                            ProfilerFeature::CPUUtilization,
+                            ProfilerFeature::CPUAllThreads,
+                            ProfilerFeature::SamplingAllThreads,
+                            ProfilerFeature::MarkersAllThreads,
+                            ProfilerFeature::UnregisteredThreads};
+  constexpr uint32_t featureCount = uint32_t(MOZ_ARRAY_LENGTH(featureList));
+
+  auto testFeatures = [&](uint32_t features,
+                          const std::string& featuresString) {
+    SCOPED_TRACE(featuresString.c_str());
+
+    ASSERT_TRUE(!profiler_is_active());
+
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+    ASSERT_TRUE(profiler_is_active());
+
+    // Write some Gecko Profiler samples.
+    EXPECT_EQ(WaitForSamplingState(),
+              (((features & ProfilerFeature::NoStackSampling) != 0) &&
+               ((features & (ProfilerFeature::CPUUtilization |
+                             ProfilerFeature::CPUAllThreads)) == 0))
+                  ? SamplingState::NoStackSamplingCompleted
+                  : SamplingState::SamplingCompleted);
+
+    // Check that the profile looks valid. Note that we don't test feature-
+    // specific changes.
+    UniquePtr<char[]> profile = profiler_get_profile();
+    JSONOutputCheck(profile.get(), [](const Json::Value& aRoot) {});
+
+    profiler_stop();
+    ASSERT_TRUE(!profiler_is_active());
+  };
+
+  testFeatures(0, "Features: (none)");
+
+  for (uint32_t f1 = 0u; f1 < featureCount; ++f1) {
+    const uint32_t features1 = featureList[f1];
+    std::string features1String = "Features: ";
+    features1String += GetFeatureName(featureList[f1]);
+
+    testFeatures(features1, features1String);
+
+    for (uint32_t f2 = f1 + 1u; f2 < featureCount; ++f2) {
+      const uint32_t features12 = f1 | featureList[f2];
+      std::string features12String = features1String + " ";
+      features12String += GetFeatureName(featureList[f2]);
+
+      testFeatures(features12, features12String);
+
+      for (uint32_t f3 = f2 + 1u; f3 < featureCount; ++f3) {
+        const uint32_t features123 = features12 | featureList[f3];
+        std::string features123String = features12String + " ";
+        features123String += GetFeatureName(featureList[f3]);
+
+        testFeatures(features123, features123String);
+      }
+    }
+  }
+}
+
+static void CountCPUDeltas(const Json::Value& aThread, size_t& aOutSamplings,
+                           uint64_t& aOutCPUDeltaSum) {
+  GET_JSON(samples, aThread["samples"], Object);
+  {
+    Json::ArrayIndex threadCPUDeltaIndex = 0;
+    GET_JSON(schema, samples["schema"], Object);
+    {
+      GET_JSON(jsonThreadCPUDeltaIndex, schema["threadCPUDelta"], UInt);
+      threadCPUDeltaIndex = jsonThreadCPUDeltaIndex.asUInt();
+    }
+
+    aOutSamplings = 0;
+    aOutCPUDeltaSum = 0;
+    GET_JSON(data, samples["data"], Array);
+    aOutSamplings = data.size();
+    for (const Json::Value& sample : data) {
+      ASSERT_TRUE(sample.isArray());
+      if (sample.isValidIndex(threadCPUDeltaIndex)) {
+        if (!sample[threadCPUDeltaIndex].isNull()) {
+          GET_JSON(cpuDelta, sample[threadCPUDeltaIndex], UInt64);
+          aOutCPUDeltaSum += uint64_t(cpuDelta.asUInt64());
+        }
+      }
+    }
+  }
+}
+
+TEST(GeckoProfiler, CPUUsage)
+{
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  const char* filters[] = {"GeckoMain", "Idle test", "Busy test"};
+
+  enum class TestThreadsState {
+    // Initial state, while constructing and starting the idle thread.
+    STARTING,
+    // Set by the idle thread just before running its main mostly-idle loop.
+    RUNNING1,
+    RUNNING2,
+    // Set by the main thread when it wants the idle thread to stop.
+    STOPPING
+  };
+  Atomic<TestThreadsState> testThreadsState{TestThreadsState::STARTING};
+
+  std::thread idle([&]() {
+    AUTO_PROFILER_REGISTER_THREAD("Idle test");
+    // Add a label to ensure that we have a non-empty stack, even if native
+    // stack-walking is not available.
+    AUTO_PROFILER_LABEL("Idle test", PROFILER);
+    ASSERT_TRUE(testThreadsState.compareExchange(TestThreadsState::STARTING,
+                                                 TestThreadsState::RUNNING1) ||
+                testThreadsState.compareExchange(TestThreadsState::RUNNING1,
+                                                 TestThreadsState::RUNNING2));
+
+    while (testThreadsState != TestThreadsState::STOPPING) {
+      // Sleep for multiple profiler intervals, so the profiler should have
+      // samples with zero CPU utilization.
+      PR_Sleep(PR_MillisecondsToInterval(PROFILER_DEFAULT_INTERVAL * 10));
+    }
+  });
+
+  std::thread busy([&]() {
+    AUTO_PROFILER_REGISTER_THREAD("Busy test");
+    // Add a label to ensure that we have a non-empty stack, even if native
+    // stack-walking is not available.
+    AUTO_PROFILER_LABEL("Busy test", PROFILER);
+    ASSERT_TRUE(testThreadsState.compareExchange(TestThreadsState::STARTING,
+                                                 TestThreadsState::RUNNING1) ||
+                testThreadsState.compareExchange(TestThreadsState::RUNNING1,
+                                                 TestThreadsState::RUNNING2));
+
+    while (testThreadsState != TestThreadsState::STOPPING) {
+      // Stay busy!
+    }
+  });
+
+  // Wait for idle thread to start running its main loop.
+  while (testThreadsState != TestThreadsState::RUNNING2) {
+    PR_Sleep(PR_MillisecondsToInterval(1));
+  }
+
+  // We want to ensure that CPU usage numbers are present whether or not we are
+  // collecting stack samples.
+  static constexpr bool scTestsWithOrWithoutStackSampling[] = {false, true};
+  for (const bool testWithNoStackSampling : scTestsWithOrWithoutStackSampling) {
+    ASSERT_TRUE(!profiler_is_active());
+    ASSERT_TRUE(!profiler_callback_after_sampling(
+        [&](SamplingState) { ASSERT_TRUE(false); }));
+
+    profiler_start(
+        PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+        ProfilerFeature::StackWalk | ProfilerFeature::CPUUtilization |
+            (testWithNoStackSampling ? ProfilerFeature::NoStackSampling : 0),
+        filters, MOZ_ARRAY_LENGTH(filters), 0);
+    // Grab a few samples, each with a different label on the stack.
+#  define SAMPLE_LABEL_PREFIX "CPUUsage sample label "
+    static constexpr const char* scSampleLabels[] = {
+        SAMPLE_LABEL_PREFIX "0", SAMPLE_LABEL_PREFIX "1",
+        SAMPLE_LABEL_PREFIX "2", SAMPLE_LABEL_PREFIX "3",
+        SAMPLE_LABEL_PREFIX "4", SAMPLE_LABEL_PREFIX "5",
+        SAMPLE_LABEL_PREFIX "6", SAMPLE_LABEL_PREFIX "7",
+        SAMPLE_LABEL_PREFIX "8", SAMPLE_LABEL_PREFIX "9"};
+    static constexpr size_t scSampleLabelCount =
+        (sizeof(scSampleLabels) / sizeof(scSampleLabels[0]));
+    // We'll do two samplings for each label.
+    static constexpr size_t scMinSamplings = scSampleLabelCount * 2;
+
+    for (const char* sampleLabel : scSampleLabels) {
+      AUTO_PROFILER_LABEL(sampleLabel, OTHER);
+      ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+      // Note: There could have been a delay before this label above, where the
+      // profiler could have sampled the stack and missed the label. By forcing
+      // another sampling now, the label is guaranteed to be present.
+      ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+    }
+
+    UniquePtr<char[]> profile = profiler_get_profile();
+
+    if (testWithNoStackSampling) {
+      // If we are testing nostacksampling, we shouldn't find this label prefix
+      // in the profile.
+      EXPECT_FALSE(strstr(profile.get(), SAMPLE_LABEL_PREFIX));
+    } else {
+      // In normal sampling mode, we should find all labels.
+      for (const char* sampleLabel : scSampleLabels) {
+        EXPECT_TRUE(strstr(profile.get(), sampleLabel));
+      }
+    }
+
+    JSONOutputCheck(profile.get(), [testWithNoStackSampling](
+                                       const Json::Value& aRoot) {
+      // Check that the "cpu" feature is present.
+      GET_JSON(meta, aRoot["meta"], Object);
+      {
+        GET_JSON(configuration, meta["configuration"], Object);
+        {
+          GET_JSON(features, configuration["features"], Array);
+          { EXPECT_JSON_ARRAY_CONTAINS(features, String, "cpu"); }
+        }
+      }
+
+      {
+        GET_JSON(sampleUnits, meta["sampleUnits"], Object);
+        {
+          EXPECT_EQ_JSON(sampleUnits["time"], String, "ms");
+          EXPECT_EQ_JSON(sampleUnits["eventDelay"], String, "ms");
+#  if defined(GP_OS_windows) || defined(GP_OS_darwin) || \
+      defined(GP_OS_linux) || defined(GP_OS_android) || defined(GP_OS_freebsd)
+          // Note: The exact string is not important here.
+          EXPECT_TRUE(sampleUnits["threadCPUDelta"].isString())
+              << "There should be a sampleUnits.threadCPUDelta on this "
+                 "platform";
+#  else
+        EXPECT_FALSE(sampleUnits.isMember("threadCPUDelta"))
+            << "Unexpected sampleUnits.threadCPUDelta on this platform";;
+#  endif
+        }
+      }
+
+      bool foundMain = false;
+      bool foundIdle = false;
+      uint64_t idleThreadCPUDeltaSum = 0u;
+      bool foundBusy = false;
+      uint64_t busyThreadCPUDeltaSum = 0u;
+
+      // Check that the sample schema contains "threadCPUDelta".
+      GET_JSON(threads, aRoot["threads"], Array);
+      for (const Json::Value& thread : threads) {
+        ASSERT_TRUE(thread.isObject());
+        GET_JSON(name, thread["name"], String);
+        if (name.asString() == "GeckoMain") {
+          foundMain = true;
+          GET_JSON(samples, thread["samples"], Object);
+          {
+            Json::ArrayIndex stackIndex = 0;
+            Json::ArrayIndex threadCPUDeltaIndex = 0;
+            GET_JSON(schema, samples["schema"], Object);
+            {
+              GET_JSON(jsonStackIndex, schema["stack"], UInt);
+              stackIndex = jsonStackIndex.asUInt();
+              GET_JSON(jsonThreadCPUDeltaIndex, schema["threadCPUDelta"], UInt);
+              threadCPUDeltaIndex = jsonThreadCPUDeltaIndex.asUInt();
+            }
+
+            std::set<uint64_t> stackLeaves;  // To count distinct leaves.
+            unsigned threadCPUDeltaCount = 0;
+            GET_JSON(data, samples["data"], Array);
+            if (testWithNoStackSampling) {
+              // When not sampling stacks, the first sampling loop will have no
+              // running times, so it won't output anything.
+              EXPECT_GE(data.size(), scMinSamplings - 1);
+            } else {
+              EXPECT_GE(data.size(), scMinSamplings);
+            }
+            for (const Json::Value& sample : data) {
+              ASSERT_TRUE(sample.isArray());
+              if (sample.isValidIndex(stackIndex)) {
+                if (!sample[stackIndex].isNull()) {
+                  GET_JSON(stack, sample[stackIndex], UInt64);
+                  stackLeaves.insert(stack.asUInt64());
+                }
+              }
+              if (sample.isValidIndex(threadCPUDeltaIndex)) {
+                if (!sample[threadCPUDeltaIndex].isNull()) {
+                  EXPECT_TRUE(sample[threadCPUDeltaIndex].isUInt64());
+                  ++threadCPUDeltaCount;
+                }
+              }
+            }
+
+            if (testWithNoStackSampling) {
+              // in nostacksampling mode, there should only be one kind of stack
+              // leaf (the root).
+              EXPECT_EQ(stackLeaves.size(), 1u);
+            } else {
+              // in normal sampling mode, there should be at least one kind of
+              // stack leaf for each distinct label.
+              EXPECT_GE(stackLeaves.size(), scSampleLabelCount);
+            }
+
+#  if defined(GP_OS_windows) || defined(GP_OS_darwin) || \
+      defined(GP_OS_linux) || defined(GP_OS_android) || defined(GP_OS_freebsd)
+            EXPECT_GE(threadCPUDeltaCount, data.size() - 1u)
+                << "There should be 'threadCPUDelta' values in all but 1 "
+                   "samples";
+#  else
+          // All "threadCPUDelta" data should be absent or null on unsupported
+          // platforms.
+          EXPECT_EQ(threadCPUDeltaCount, 0u);
+#  endif
+          }
+        } else if (name.asString() == "Idle test") {
+          foundIdle = true;
+          size_t samplings;
+          CountCPUDeltas(thread, samplings, idleThreadCPUDeltaSum);
+          if (testWithNoStackSampling) {
+            // When not sampling stacks, the first sampling loop will have no
+            // running times, so it won't output anything.
+            EXPECT_GE(samplings, scMinSamplings - 1);
+          } else {
+            EXPECT_GE(samplings, scMinSamplings);
+          }
+#  if !(defined(GP_OS_windows) || defined(GP_OS_darwin) || \
+        defined(GP_OS_linux) || defined(GP_OS_android) ||  \
+        defined(GP_OS_freebsd))
+          // All "threadCPUDelta" data should be absent or null on unsupported
+          // platforms.
+          EXPECT_EQ(idleThreadCPUDeltaSum, 0u);
+#  endif
+        } else if (name.asString() == "Busy test") {
+          foundBusy = true;
+          size_t samplings;
+          CountCPUDeltas(thread, samplings, busyThreadCPUDeltaSum);
+          if (testWithNoStackSampling) {
+            // When not sampling stacks, the first sampling loop will have no
+            // running times, so it won't output anything.
+            EXPECT_GE(samplings, scMinSamplings - 1);
+          } else {
+            EXPECT_GE(samplings, scMinSamplings);
+          }
+#  if !(defined(GP_OS_windows) || defined(GP_OS_darwin) || \
+        defined(GP_OS_linux) || defined(GP_OS_android) ||  \
+        defined(GP_OS_freebsd))
+          // All "threadCPUDelta" data should be absent or null on unsupported
+          // platforms.
+          EXPECT_EQ(busyThreadCPUDeltaSum, 0u);
+#  endif
+        }
+      }
+
+      EXPECT_TRUE(foundMain);
+      EXPECT_TRUE(foundIdle);
+      EXPECT_TRUE(foundBusy);
+      EXPECT_LE(idleThreadCPUDeltaSum, busyThreadCPUDeltaSum);
+    });
+
+    // Note: There is no non-racy way to test for SamplingState::JustStopped, as
+    // it would require coordination between `profiler_stop()` and another
+    // thread doing `profiler_callback_after_sampling()` at just the right
+    // moment.
+
+    profiler_stop();
+    ASSERT_TRUE(!profiler_is_active());
+    ASSERT_TRUE(!profiler_callback_after_sampling(
+        [&](SamplingState) { ASSERT_TRUE(false); }));
+  }
+
+  testThreadsState = TestThreadsState::STOPPING;
+  busy.join();
+  idle.join();
+}
+
+TEST(GeckoProfiler, AllThreads)
+{
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  ASSERT_EQ(static_cast<uint32_t>(ThreadProfilingFeatures::Any), 1u + 2u + 4u)
+      << "This test assumes that there are 3 binary choices 1+2+4; "
+         "Is this test up to date?";
+
+  for (uint32_t threadFeaturesBinary = 0u;
+       threadFeaturesBinary <=
+       static_cast<uint32_t>(ThreadProfilingFeatures::Any);
+       ++threadFeaturesBinary) {
+    ThreadProfilingFeatures threadFeatures =
+        static_cast<ThreadProfilingFeatures>(threadFeaturesBinary);
+    const bool threadCPU = DoFeaturesIntersect(
+        threadFeatures, ThreadProfilingFeatures::CPUUtilization);
+    const bool threadSampling =
+        DoFeaturesIntersect(threadFeatures, ThreadProfilingFeatures::Sampling);
+    const bool threadMarkers =
+        DoFeaturesIntersect(threadFeatures, ThreadProfilingFeatures::Markers);
+
+    ASSERT_TRUE(!profiler_is_active());
+
+    uint32_t features = ProfilerFeature::StackWalk;
+    std::string featuresString = "Features: StackWalk Threads";
+    if (threadCPU) {
+      features |= ProfilerFeature::CPUAllThreads;
+      featuresString += " CPUAllThreads";
+    }
+    if (threadSampling) {
+      features |= ProfilerFeature::SamplingAllThreads;
+      featuresString += " SamplingAllThreads";
+    }
+    if (threadMarkers) {
+      features |= ProfilerFeature::MarkersAllThreads;
+      featuresString += " MarkersAllThreads";
+    }
+
+    SCOPED_TRACE(featuresString.c_str());
+
+    const char* filters[] = {"GeckoMain", "Selected"};
+
+    EXPECT_FALSE(profiler_thread_is_being_profiled(
+        ThreadProfilingFeatures::CPUUtilization));
+    EXPECT_FALSE(
+        profiler_thread_is_being_profiled(ThreadProfilingFeatures::Sampling));
+    EXPECT_FALSE(
+        profiler_thread_is_being_profiled(ThreadProfilingFeatures::Markers));
+    EXPECT_FALSE(profiler_thread_is_being_profiled_for_markers());
+
+    profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL,
+                   features, filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+    EXPECT_TRUE(profiler_thread_is_being_profiled(
+        ThreadProfilingFeatures::CPUUtilization));
+    EXPECT_TRUE(
+        profiler_thread_is_being_profiled(ThreadProfilingFeatures::Sampling));
+    EXPECT_TRUE(
+        profiler_thread_is_being_profiled(ThreadProfilingFeatures::Markers));
+    EXPECT_TRUE(profiler_thread_is_being_profiled_for_markers());
+
+    // This will signal all threads to stop spinning.
+    Atomic<bool> stopThreads{false};
+
+    Atomic<int> selectedThreadSpins{0};
+    std::thread selectedThread([&]() {
+      AUTO_PROFILER_REGISTER_THREAD("Selected test thread");
+      // Add a label to ensure that we have a non-empty stack, even if native
+      // stack-walking is not available.
+      AUTO_PROFILER_LABEL("Selected test thread", PROFILER);
+      EXPECT_TRUE(profiler_thread_is_being_profiled(
+          ThreadProfilingFeatures::CPUUtilization));
+      EXPECT_TRUE(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Sampling));
+      EXPECT_TRUE(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Markers));
+      EXPECT_TRUE(profiler_thread_is_being_profiled_for_markers());
+      while (!stopThreads) {
+        PROFILER_MARKER_UNTYPED("Spinning Selected!", PROFILER);
+        ++selectedThreadSpins;
+        PR_Sleep(PR_MillisecondsToInterval(1));
+      }
+    });
+
+    Atomic<int> unselectedThreadSpins{0};
+    std::thread unselectedThread([&]() {
+      AUTO_PROFILER_REGISTER_THREAD("Registered test thread");
+      // Add a label to ensure that we have a non-empty stack, even if native
+      // stack-walking is not available.
+      AUTO_PROFILER_LABEL("Registered test thread", PROFILER);
+      // This thread is *not* selected for full profiling, but it may still be
+      // profiled depending on the -allthreads features.
+      EXPECT_EQ(profiler_thread_is_being_profiled(
+                    ThreadProfilingFeatures::CPUUtilization),
+                threadCPU);
+      EXPECT_EQ(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Sampling),
+          threadSampling);
+      EXPECT_EQ(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Markers),
+          threadMarkers);
+      EXPECT_EQ(profiler_thread_is_being_profiled_for_markers(), threadMarkers);
+      while (!stopThreads) {
+        PROFILER_MARKER_UNTYPED("Spinning Registered!", PROFILER);
+        ++unselectedThreadSpins;
+        PR_Sleep(PR_MillisecondsToInterval(1));
+      }
+    });
+
+    Atomic<int> unregisteredThreadSpins{0};
+    std::thread unregisteredThread([&]() {
+      // No `AUTO_PROFILER_REGISTER_THREAD` here.
+      EXPECT_FALSE(profiler_thread_is_being_profiled(
+          ThreadProfilingFeatures::CPUUtilization));
+      EXPECT_FALSE(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Sampling));
+      EXPECT_FALSE(
+          profiler_thread_is_being_profiled(ThreadProfilingFeatures::Markers));
+      EXPECT_FALSE(profiler_thread_is_being_profiled_for_markers());
+      while (!stopThreads) {
+        PROFILER_MARKER_UNTYPED("Spinning Unregistered!", PROFILER);
+        ++unregisteredThreadSpins;
+        PR_Sleep(PR_MillisecondsToInterval(1));
+      }
+    });
+
+    // Wait for all threads to have started at least one spin.
+    while (selectedThreadSpins == 0 || unselectedThreadSpins == 0 ||
+           unregisteredThreadSpins == 0) {
+      PR_Sleep(PR_MillisecondsToInterval(1));
+    }
+
+    // Wait until the sampler has done at least one loop.
+    ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+
+    // Restart the spin counts, and ensure each threads will do at least one
+    // more spin each. Since spins are increased after PROFILER_MARKER calls, in
+    // the worst case, each thread will have attempted to record at least one
+    // marker.
+    selectedThreadSpins = 0;
+    unselectedThreadSpins = 0;
+    unregisteredThreadSpins = 0;
+    while (selectedThreadSpins < 1 && unselectedThreadSpins < 1 &&
+           unregisteredThreadSpins < 1) {
+      ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+    }
+
+    profiler_pause();
+    UniquePtr<char[]> profile = profiler_get_profile();
+
+    profiler_stop();
+    stopThreads = true;
+    unregisteredThread.join();
+    unselectedThread.join();
+    selectedThread.join();
+
+    JSONOutputCheck(profile.get(), [&](const Json::Value& aRoot) {
+      GET_JSON(threads, aRoot["threads"], Array);
+      int foundMain = 0;
+      int foundSelected = 0;
+      int foundSelectedMarker = 0;
+      int foundUnselected = 0;
+      int foundUnselectedMarker = 0;
+      for (const Json::Value& thread : threads) {
+        ASSERT_TRUE(thread.isObject());
+        GET_JSON(stringTable, thread["stringTable"], Array);
+        GET_JSON(name, thread["name"], String);
+        if (name.asString() == "GeckoMain") {
+          ++foundMain;
+          // Don't check the main thread further in this test.
+
+        } else if (name.asString() == "Selected test thread") {
+          ++foundSelected;
+
+          GET_JSON(samples, thread["samples"], Object);
+          GET_JSON(samplesData, samples["data"], Array);
+          EXPECT_GT(samplesData.size(), 0u);
+
+          GET_JSON(markers, thread["markers"], Object);
+          GET_JSON(markersData, markers["data"], Array);
+          for (const Json::Value& marker : markersData) {
+            const unsigned int NAME = 0u;
+            ASSERT_TRUE(marker[NAME].isUInt());  // name id
+            GET_JSON(name, stringTable[marker[NAME].asUInt()], String);
+            if (name == "Spinning Selected!") {
+              ++foundSelectedMarker;
+            }
+          }
+        } else if (name.asString() == "Registered test thread") {
+          ++foundUnselected;
+
+          GET_JSON(samples, thread["samples"], Object);
+          GET_JSON(samplesData, samples["data"], Array);
+          if (threadCPU || threadSampling) {
+            EXPECT_GT(samplesData.size(), 0u);
+          } else {
+            EXPECT_EQ(samplesData.size(), 0u);
+          }
+
+          GET_JSON(markers, thread["markers"], Object);
+          GET_JSON(markersData, markers["data"], Array);
+          for (const Json::Value& marker : markersData) {
+            const unsigned int NAME = 0u;
+            ASSERT_TRUE(marker[NAME].isUInt());  // name id
+            GET_JSON(name, stringTable[marker[NAME].asUInt()], String);
+            if (name == "Spinning Registered!") {
+              ++foundUnselectedMarker;
+            }
+          }
+
+        } else {
+          EXPECT_STRNE(name.asString().c_str(),
+                       "Unregistered test thread label");
+        }
+      }
+      EXPECT_EQ(foundMain, 1);
+      EXPECT_EQ(foundSelected, 1);
+      EXPECT_GT(foundSelectedMarker, 0);
+      EXPECT_EQ(foundUnselected,
+                (threadCPU || threadSampling || threadMarkers) ? 1 : 0)
+          << "Unselected thread should only be present if at least one of the "
+             "allthreads feature is on";
+      if (threadMarkers) {
+        EXPECT_GT(foundUnselectedMarker, 0);
+      } else {
+        EXPECT_EQ(foundUnselectedMarker, 0);
+      }
+    });
+  }
+}
+
+TEST(GeckoProfiler, FailureHandling)
+{
+  profiler_init_main_thread_id();
+  ASSERT_TRUE(profiler_is_main_thread())
+  << "This test assumes it runs on the main thread";
+
+  uint32_t features = ProfilerFeature::StackWalk;
+  const char* filters[] = {"GeckoMain"};
+  profiler_start(PROFILER_DEFAULT_ENTRIES, PROFILER_DEFAULT_INTERVAL, features,
+                 filters, MOZ_ARRAY_LENGTH(filters), 0);
+
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+
+  // User-defined marker type that generates a failure when streaming JSON.
+  struct GtestFailingMarker {
+    static constexpr Span<const char> MarkerTypeName() {
+      return MakeStringSpan("markers-gtest-failing");
+    }
+    static void StreamJSONMarkerData(
+        mozilla::baseprofiler::SpliceableJSONWriter& aWriter) {
+      aWriter.SetFailure("boom!");
+    }
+    static mozilla::MarkerSchema MarkerTypeDisplay() {
+      return mozilla::MarkerSchema::SpecialFrontendLocation{};
+    }
+  };
+  EXPECT_TRUE(profiler_add_marker("Gtest failing marker",
+                                  geckoprofiler::category::OTHER, {},
+                                  GtestFailingMarker{}));
+
+  ASSERT_EQ(WaitForSamplingState(), SamplingState::SamplingCompleted);
+  profiler_pause();
+
+  FailureLatchSource failureLatch;
+  SpliceableChunkedJSONWriter w{failureLatch};
+  EXPECT_FALSE(w.Failed());
+  ASSERT_FALSE(w.GetFailure());
+
+  w.Start();
+  EXPECT_FALSE(w.Failed());
+  ASSERT_FALSE(w.GetFailure());
+
+  // The marker will cause a failure during this function call.
+  EXPECT_FALSE(::profiler_stream_json_for_this_process(w));
+  EXPECT_TRUE(w.Failed());
+  ASSERT_TRUE(w.GetFailure());
+  EXPECT_EQ(strcmp(w.GetFailure(), "boom!"), 0);
+
+  // Already failed, check that we don't crash or reset the failure.
+  EXPECT_FALSE(::profiler_stream_json_for_this_process(w));
+  EXPECT_TRUE(w.Failed());
+  ASSERT_TRUE(w.GetFailure());
+  EXPECT_EQ(strcmp(w.GetFailure(), "boom!"), 0);
+
+  w.End();
+
+  profiler_stop();
+
+  EXPECT_TRUE(w.Failed());
+  ASSERT_TRUE(w.GetFailure());
+  EXPECT_EQ(strcmp(w.GetFailure(), "boom!"), 0);
+
+  UniquePtr<char[]> profile = w.ChunkedWriteFunc().CopyData();
+  ASSERT_EQ(profile.get(), nullptr);
+}
+
+#endif  // MOZ_GECKO_PROFILER