Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 742 insertions, 0 deletions

diff --git a/xpcom/base/nsMemoryInfoDumper.cpp b/xpcom/base/nsMemoryInfoDumper.cpp
new file mode 100644
index 0000000000..28af408178
--- /dev/null
+++ b/xpcom/base/nsMemoryInfoDumper.cpp
@@ -0,0 +1,742 @@
+/* -*- Mode: C++; tab-width: 8; 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/. */
+
+#include "mozilla/JSONWriter.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/nsMemoryInfoDumper.h"
+#include "mozilla/DebugOnly.h"
+#include "nsDumpUtils.h"
+
+#include "mozilla/Unused.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/ContentChild.h"
+#include "nsIConsoleService.h"
+#include "nsCycleCollector.h"
+#include "nsICycleCollectorListener.h"
+#include "nsIMemoryReporter.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsGZFileWriter.h"
+#include "nsJSEnvironment.h"
+#include "nsPrintfCString.h"
+#include "nsServiceManagerUtils.h"
+#include "nsIFile.h"
+
+#ifdef XP_WIN
+#  include <process.h>
+#  ifndef getpid
+#    define getpid _getpid
+#  endif
+#else
+#  include <unistd.h>
+#endif
+
+#ifdef XP_UNIX
+#  define MOZ_SUPPORTS_FIFO 1
+#endif
+
+// Some Android devices seem to send RT signals to Firefox so we want to avoid
+// consuming those as they're not user triggered.
+#if !defined(ANDROID) && (defined(XP_LINUX) || defined(__FreeBSD__))
+#  define MOZ_SUPPORTS_RT_SIGNALS 1
+#endif
+
+#if defined(MOZ_SUPPORTS_RT_SIGNALS)
+#  include <fcntl.h>
+#  include <sys/types.h>
+#  include <sys/stat.h>
+#endif
+
+#if defined(MOZ_SUPPORTS_FIFO)
+#  include "mozilla/Preferences.h"
+#endif
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+namespace {
+
+class DumpMemoryInfoToTempDirRunnable : public Runnable {
+ public:
+  DumpMemoryInfoToTempDirRunnable(const nsAString& aIdentifier, bool aAnonymize,
+                                  bool aMinimizeMemoryUsage)
+      : mozilla::Runnable("DumpMemoryInfoToTempDirRunnable"),
+        mIdentifier(aIdentifier),
+        mAnonymize(aAnonymize),
+        mMinimizeMemoryUsage(aMinimizeMemoryUsage) {}
+
+  NS_IMETHOD Run() override {
+    nsCOMPtr<nsIMemoryInfoDumper> dumper =
+        do_GetService("@mozilla.org/memory-info-dumper;1");
+    dumper->DumpMemoryInfoToTempDir(mIdentifier, mAnonymize,
+                                    mMinimizeMemoryUsage);
+    return NS_OK;
+  }
+
+ private:
+  const nsString mIdentifier;
+  const bool mAnonymize;
+  const bool mMinimizeMemoryUsage;
+};
+
+class GCAndCCLogDumpRunnable final : public Runnable,
+                                     public nsIDumpGCAndCCLogsCallback {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  GCAndCCLogDumpRunnable(const nsAString& aIdentifier, bool aDumpAllTraces,
+                         bool aDumpChildProcesses)
+      : mozilla::Runnable("GCAndCCLogDumpRunnable"),
+        mIdentifier(aIdentifier),
+        mDumpAllTraces(aDumpAllTraces),
+        mDumpChildProcesses(aDumpChildProcesses) {}
+
+  NS_IMETHOD Run() override {
+    nsCOMPtr<nsIMemoryInfoDumper> dumper =
+        do_GetService("@mozilla.org/memory-info-dumper;1");
+
+    dumper->DumpGCAndCCLogsToFile(mIdentifier, mDumpAllTraces,
+                                  mDumpChildProcesses, this);
+    return NS_OK;
+  }
+
+  NS_IMETHOD OnDump(nsIFile* aGCLog, nsIFile* aCCLog, bool aIsParent) override {
+    return NS_OK;
+  }
+
+  NS_IMETHOD OnFinish() override { return NS_OK; }
+
+ private:
+  ~GCAndCCLogDumpRunnable() = default;
+
+  const nsString mIdentifier;
+  const bool mDumpAllTraces;
+  const bool mDumpChildProcesses;
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(GCAndCCLogDumpRunnable, Runnable,
+                            nsIDumpGCAndCCLogsCallback)
+
+}  // namespace
+
+#if defined(MOZ_SUPPORTS_RT_SIGNALS)  // {
+namespace {
+
+/*
+ * The following code supports dumping about:memory upon receiving a signal.
+ *
+ * We listen for the following signals:
+ *
+ *  - SIGRTMIN:     Dump our memory reporters (and those of our child
+ *                  processes),
+ *  - SIGRTMIN + 1: Dump our memory reporters (and those of our child
+ *                  processes) after minimizing memory usage, and
+ *  - SIGRTMIN + 2: Dump the GC and CC logs in this and our child processes.
+ *
+ * When we receive one of these signals, we write the signal number to a pipe.
+ * The IO thread then notices that the pipe has been written to, and kicks off
+ * the appropriate task on the main thread.
+ *
+ * This scheme is similar to using signalfd(), except it's portable and it
+ * doesn't require the use of sigprocmask, which is problematic because it
+ * masks signals received by child processes.
+ *
+ * In theory, we could use Chromium's MessageLoopForIO::CatchSignal() for this.
+ * But that uses libevent, which does not handle the realtime signals (bug
+ * 794074).
+ */
+
+// It turns out that at least on some systems, SIGRTMIN is not a compile-time
+// constant, so these have to be set at runtime.
+static uint8_t sDumpAboutMemorySignum;          // SIGRTMIN
+static uint8_t sDumpAboutMemoryAfterMMUSignum;  // SIGRTMIN + 1
+static uint8_t sGCAndCCDumpSignum;              // SIGRTMIN + 2
+
+void doMemoryReport(const uint8_t aRecvSig) {
+  // Dump our memory reports (but run this on the main thread!).
+  bool minimize = aRecvSig == sDumpAboutMemoryAfterMMUSignum;
+  LOG("SignalWatcher(sig %d) dispatching memory report runnable.", aRecvSig);
+  RefPtr<DumpMemoryInfoToTempDirRunnable> runnable =
+      new DumpMemoryInfoToTempDirRunnable(/* identifier = */ u""_ns,
+                                          /* anonymize = */ false, minimize);
+  NS_DispatchToMainThread(runnable);
+}
+
+void doGCCCDump(const uint8_t aRecvSig) {
+  LOG("SignalWatcher(sig %d) dispatching GC/CC log runnable.", aRecvSig);
+  // Dump GC and CC logs (from the main thread).
+  RefPtr<GCAndCCLogDumpRunnable> runnable =
+      new GCAndCCLogDumpRunnable(/* identifier = */ u""_ns,
+                                 /* allTraces = */ true,
+                                 /* dumpChildProcesses = */ true);
+  NS_DispatchToMainThread(runnable);
+}
+
+}  // namespace
+#endif  // MOZ_SUPPORTS_RT_SIGNALS }
+
+#if defined(MOZ_SUPPORTS_FIFO)  // {
+namespace {
+
+void doMemoryReport(const nsCString& aInputStr) {
+  bool minimize = aInputStr.EqualsLiteral("minimize memory report");
+  LOG("FifoWatcher(command:%s) dispatching memory report runnable.",
+      aInputStr.get());
+  RefPtr<DumpMemoryInfoToTempDirRunnable> runnable =
+      new DumpMemoryInfoToTempDirRunnable(/* identifier = */ u""_ns,
+                                          /* anonymize = */ false, minimize);
+  NS_DispatchToMainThread(runnable);
+}
+
+void doGCCCDump(const nsCString& aInputStr) {
+  bool doAllTracesGCCCDump = aInputStr.EqualsLiteral("gc log");
+  LOG("FifoWatcher(command:%s) dispatching GC/CC log runnable.",
+      aInputStr.get());
+  RefPtr<GCAndCCLogDumpRunnable> runnable = new GCAndCCLogDumpRunnable(
+      /* identifier = */ u""_ns, doAllTracesGCCCDump,
+      /* dumpChildProcesses = */ true);
+  NS_DispatchToMainThread(runnable);
+}
+
+bool SetupFifo() {
+#  ifdef DEBUG
+  static bool fifoCallbacksRegistered = false;
+#  endif
+
+  if (!FifoWatcher::MaybeCreate()) {
+    return false;
+  }
+
+  MOZ_ASSERT(!fifoCallbacksRegistered,
+             "FifoWatcher callbacks should be registered only once");
+
+  FifoWatcher* fw = FifoWatcher::GetSingleton();
+  // Dump our memory reports (but run this on the main thread!).
+  fw->RegisterCallback("memory report"_ns, doMemoryReport);
+  fw->RegisterCallback("minimize memory report"_ns, doMemoryReport);
+  // Dump GC and CC logs (from the main thread).
+  fw->RegisterCallback("gc log"_ns, doGCCCDump);
+  fw->RegisterCallback("abbreviated gc log"_ns, doGCCCDump);
+
+#  ifdef DEBUG
+  fifoCallbacksRegistered = true;
+#  endif
+  return true;
+}
+
+void OnFifoEnabledChange(const char* /*unused*/, void* /*unused*/) {
+  LOG("%s changed", FifoWatcher::kPrefName);
+  if (SetupFifo()) {
+    Preferences::UnregisterCallback(OnFifoEnabledChange,
+                                    FifoWatcher::kPrefName);
+  }
+}
+
+}  // namespace
+#endif  // MOZ_SUPPORTS_FIFO }
+
+NS_IMPL_ISUPPORTS(nsMemoryInfoDumper, nsIMemoryInfoDumper)
+
+nsMemoryInfoDumper::nsMemoryInfoDumper() = default;
+
+nsMemoryInfoDumper::~nsMemoryInfoDumper() = default;
+
+/* static */
+void nsMemoryInfoDumper::Initialize() {
+#if defined(MOZ_SUPPORTS_RT_SIGNALS)
+  SignalPipeWatcher* sw = SignalPipeWatcher::GetSingleton();
+
+  // Dump memory reporters (and those of our child processes)
+  sDumpAboutMemorySignum = SIGRTMIN;
+  sw->RegisterCallback(sDumpAboutMemorySignum, doMemoryReport);
+  // Dump our memory reporters after minimizing memory usage
+  sDumpAboutMemoryAfterMMUSignum = SIGRTMIN + 1;
+  sw->RegisterCallback(sDumpAboutMemoryAfterMMUSignum, doMemoryReport);
+  // Dump the GC and CC logs in this and our child processes.
+  sGCAndCCDumpSignum = SIGRTMIN + 2;
+  sw->RegisterCallback(sGCAndCCDumpSignum, doGCCCDump);
+#endif
+
+#if defined(MOZ_SUPPORTS_FIFO)
+  if (!SetupFifo()) {
+    // NB: This gets loaded early enough that it's possible there is a user pref
+    //     set to enable the fifo watcher that has not been loaded yet. Register
+    //     to attempt to initialize if the fifo watcher becomes enabled by
+    //     a user pref.
+    Preferences::RegisterCallback(OnFifoEnabledChange, FifoWatcher::kPrefName);
+  }
+#endif
+}
+
+static void EnsureNonEmptyIdentifier(nsAString& aIdentifier) {
+  if (!aIdentifier.IsEmpty()) {
+    return;
+  }
+
+  // If the identifier is empty, set it to the number of whole seconds since the
+  // epoch.  This identifier will appear in the files that this process
+  // generates and also the files generated by this process's children, allowing
+  // us to identify which files are from the same memory report request.
+  aIdentifier.AppendInt(static_cast<int64_t>(PR_Now()) / 1000000);
+}
+
+// Use XPCOM refcounting to fire |onFinish| when all reference-holders
+// (remote dump actors or the |DumpGCAndCCLogsToFile| activation itself)
+// have gone away.
+class nsDumpGCAndCCLogsCallbackHolder final
+    : public nsIDumpGCAndCCLogsCallback {
+ public:
+  NS_DECL_ISUPPORTS
+
+  explicit nsDumpGCAndCCLogsCallbackHolder(
+      nsIDumpGCAndCCLogsCallback* aCallback)
+      : mCallback(aCallback) {}
+
+  NS_IMETHOD OnFinish() override { return NS_ERROR_UNEXPECTED; }
+
+  NS_IMETHOD OnDump(nsIFile* aGCLog, nsIFile* aCCLog, bool aIsParent) override {
+    return mCallback->OnDump(aGCLog, aCCLog, aIsParent);
+  }
+
+ private:
+  ~nsDumpGCAndCCLogsCallbackHolder() { Unused << mCallback->OnFinish(); }
+
+  nsCOMPtr<nsIDumpGCAndCCLogsCallback> mCallback;
+};
+
+NS_IMPL_ISUPPORTS(nsDumpGCAndCCLogsCallbackHolder, nsIDumpGCAndCCLogsCallback)
+
+NS_IMETHODIMP
+nsMemoryInfoDumper::DumpGCAndCCLogsToFile(
+    const nsAString& aIdentifier, bool aDumpAllTraces, bool aDumpChildProcesses,
+    nsIDumpGCAndCCLogsCallback* aCallback) {
+  nsString identifier(aIdentifier);
+  EnsureNonEmptyIdentifier(identifier);
+  nsCOMPtr<nsIDumpGCAndCCLogsCallback> callbackHolder =
+      new nsDumpGCAndCCLogsCallbackHolder(aCallback);
+
+  if (aDumpChildProcesses) {
+    nsTArray<ContentParent*> children;
+    ContentParent::GetAll(children);
+    for (uint32_t i = 0; i < children.Length(); i++) {
+      ContentParent* cp = children[i];
+      nsCOMPtr<nsICycleCollectorLogSink> logSink =
+          nsCycleCollector_createLogSink();
+
+      logSink->SetFilenameIdentifier(identifier);
+      logSink->SetProcessIdentifier(cp->Pid());
+
+      Unused << cp->CycleCollectWithLogs(aDumpAllTraces, logSink,
+                                         callbackHolder);
+    }
+  }
+
+  nsCOMPtr<nsICycleCollectorListener> logger = nsCycleCollector_createLogger();
+
+  if (aDumpAllTraces) {
+    nsCOMPtr<nsICycleCollectorListener> allTracesLogger;
+    logger->AllTraces(getter_AddRefs(allTracesLogger));
+    logger = allTracesLogger;
+  }
+
+  nsCOMPtr<nsICycleCollectorLogSink> logSink;
+  logger->GetLogSink(getter_AddRefs(logSink));
+
+  logSink->SetFilenameIdentifier(identifier);
+
+  nsJSContext::CycleCollectNow(CCReason::DUMP_HEAP, logger);
+
+  nsCOMPtr<nsIFile> gcLog, ccLog;
+  logSink->GetGcLog(getter_AddRefs(gcLog));
+  logSink->GetCcLog(getter_AddRefs(ccLog));
+  callbackHolder->OnDump(gcLog, ccLog, /* parent = */ true);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMemoryInfoDumper::DumpGCAndCCLogsToSink(bool aDumpAllTraces,
+                                          nsICycleCollectorLogSink* aSink) {
+  nsCOMPtr<nsICycleCollectorListener> logger = nsCycleCollector_createLogger();
+
+  if (aDumpAllTraces) {
+    nsCOMPtr<nsICycleCollectorListener> allTracesLogger;
+    logger->AllTraces(getter_AddRefs(allTracesLogger));
+    logger = allTracesLogger;
+  }
+
+  logger->SetLogSink(aSink);
+
+  nsJSContext::CycleCollectNow(CCReason::DUMP_HEAP, logger);
+
+  return NS_OK;
+}
+
+static void MakeFilename(const char* aPrefix, const nsAString& aIdentifier,
+                         int aPid, const char* aSuffix, nsACString& aResult) {
+  aResult =
+      nsPrintfCString("%s-%s-%d.%s", aPrefix,
+                      NS_ConvertUTF16toUTF8(aIdentifier).get(), aPid, aSuffix);
+}
+
+// This class wraps GZFileWriter so it can be used with JSONWriter, overcoming
+// the following two problems:
+// - It provides a JSONWriterFunc::Write() that calls nsGZFileWriter::Write().
+// - It can be stored as a UniquePtr, whereas nsGZFileWriter is refcounted.
+class GZWriterWrapper final : public JSONWriteFunc {
+ public:
+  explicit GZWriterWrapper(nsGZFileWriter* aGZWriter) : mGZWriter(aGZWriter) {}
+
+  void Write(const Span<const char>& aStr) final {
+    // Ignore any failure because JSONWriteFunc doesn't have a mechanism for
+    // handling errors.
+    Unused << mGZWriter->Write(aStr.data(), aStr.size());
+  }
+
+  nsresult Finish() { return mGZWriter->Finish(); }
+
+ private:
+  RefPtr<nsGZFileWriter> mGZWriter;
+};
+
+// We need two callbacks: one that handles reports, and one that is called at
+// the end of reporting. Both the callbacks need access to the same JSONWriter,
+// so we implement both of them in this one class.
+class HandleReportAndFinishReportingCallbacks final
+    : public nsIHandleReportCallback,
+      public nsIFinishReportingCallback {
+ public:
+  NS_DECL_ISUPPORTS
+
+  HandleReportAndFinishReportingCallbacks(
+      UniquePtr<JSONWriter> aWriter, nsIFinishDumpingCallback* aFinishDumping,
+      nsISupports* aFinishDumpingData)
+      : mWriter(std::move(aWriter)),
+        mFinishDumping(aFinishDumping),
+        mFinishDumpingData(aFinishDumpingData) {}
+
+  // This is the callback for nsIHandleReportCallback.
+  NS_IMETHOD Callback(const nsACString& aProcess, const nsACString& aPath,
+                      int32_t aKind, int32_t aUnits, int64_t aAmount,
+                      const nsACString& aDescription,
+                      nsISupports* aData) override {
+    nsAutoCString process;
+    if (aProcess.IsEmpty()) {
+      // If the process is empty, the report originated with the process doing
+      // the dumping.  In that case, generate the process identifier, which is
+      // of the form "$PROCESS_NAME (pid $PID)", or just "(pid $PID)" if we
+      // don't have a process name.  If we're the main process, we let
+      // $PROCESS_NAME be "Main Process".
+      //
+      // `appendAboutMemoryMain()` in aboutMemory.js does much the same thing
+      // for live memory reports.
+      if (XRE_IsParentProcess()) {
+        // We're the main process.
+        process.AssignLiteral("Main Process");
+      } else if (ContentChild* cc = ContentChild::GetSingleton()) {
+        // Try to get the process name from ContentChild.
+        cc->GetProcessName(process);
+      }
+      ContentChild::AppendProcessId(process);
+
+    } else {
+      // Otherwise, the report originated with another process and already has a
+      // process name.  Just use that.
+      process = aProcess;
+    }
+
+    mWriter->StartObjectElement();
+    {
+      mWriter->StringProperty("process", process);
+      mWriter->StringProperty("path", PromiseFlatCString(aPath));
+      mWriter->IntProperty("kind", aKind);
+      mWriter->IntProperty("units", aUnits);
+      mWriter->IntProperty("amount", aAmount);
+      mWriter->StringProperty("description", PromiseFlatCString(aDescription));
+    }
+    mWriter->EndObject();
+
+    return NS_OK;
+  }
+
+  // This is the callback for nsIFinishReportingCallback.
+  NS_IMETHOD Callback(nsISupports* aData) override {
+    mWriter->EndArray();  // end of "reports" array
+    mWriter->End();
+
+    // The call to Finish() deallocates the memory allocated by the first Write
+    // call. Because that memory was live while the memory reporters ran and
+    // was measured by them -- by "heap-allocated" if nothing else -- we want
+    // DMD to see it as well. So we deliberately don't call Finish() until
+    // after DMD finishes.
+    nsresult rv = static_cast<GZWriterWrapper&>(mWriter->WriteFunc()).Finish();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (!mFinishDumping) {
+      return NS_OK;
+    }
+
+    return mFinishDumping->Callback(mFinishDumpingData);
+  }
+
+ private:
+  ~HandleReportAndFinishReportingCallbacks() = default;
+
+  UniquePtr<JSONWriter> mWriter;
+  nsCOMPtr<nsIFinishDumpingCallback> mFinishDumping;
+  nsCOMPtr<nsISupports> mFinishDumpingData;
+};
+
+NS_IMPL_ISUPPORTS(HandleReportAndFinishReportingCallbacks,
+                  nsIHandleReportCallback, nsIFinishReportingCallback)
+
+class TempDirFinishCallback final : public nsIFinishDumpingCallback {
+ public:
+  NS_DECL_ISUPPORTS
+
+  TempDirFinishCallback(nsIFile* aReportsTmpFile,
+                        const nsCString& aReportsFinalFilename)
+      : mReportsTmpFile(aReportsTmpFile),
+        mReportsFilename(aReportsFinalFilename) {}
+
+  NS_IMETHOD Callback(nsISupports* aData) override {
+    // Rename the memory reports file, now that we're done writing all the
+    // files. Its final name is "memory-report<-identifier>-<pid>.json.gz".
+
+    nsCOMPtr<nsIFile> reportsFinalFile;
+    nsresult rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR,
+                                         getter_AddRefs(reportsFinalFile));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+#ifdef ANDROID
+    rv = reportsFinalFile->AppendNative("memory-reports"_ns);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+#endif
+
+    rv = reportsFinalFile->AppendNative(mReportsFilename);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    rv = reportsFinalFile->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0600);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsAutoString reportsFinalFilename;
+    rv = reportsFinalFile->GetLeafName(reportsFinalFilename);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    rv = mReportsTmpFile->MoveTo(/* directory */ nullptr, reportsFinalFilename);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    // Write a message to the console.
+
+    nsCOMPtr<nsIConsoleService> cs =
+        do_GetService(NS_CONSOLESERVICE_CONTRACTID, &rv);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsString path;
+    mReportsTmpFile->GetPath(path);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsString msg = u"nsIMemoryInfoDumper dumped reports to "_ns;
+    msg.Append(path);
+    return cs->LogStringMessage(msg.get());
+  }
+
+ private:
+  ~TempDirFinishCallback() = default;
+
+  nsCOMPtr<nsIFile> mReportsTmpFile;
+  nsCString mReportsFilename;
+};
+
+NS_IMPL_ISUPPORTS(TempDirFinishCallback, nsIFinishDumpingCallback)
+
+static nsresult DumpMemoryInfoToFile(nsIFile* aReportsFile,
+                                     nsIFinishDumpingCallback* aFinishDumping,
+                                     nsISupports* aFinishDumpingData,
+                                     bool aAnonymize, bool aMinimizeMemoryUsage,
+                                     nsAString& aDMDIdentifier) {
+  RefPtr<nsGZFileWriter> gzWriter = new nsGZFileWriter();
+  nsresult rv = gzWriter->Init(aReportsFile);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  auto jsonWriter =
+      MakeUnique<JSONWriter>(MakeUnique<GZWriterWrapper>(gzWriter));
+
+  nsCOMPtr<nsIMemoryReporterManager> mgr =
+      do_GetService("@mozilla.org/memory-reporter-manager;1");
+
+  // This is the first write to the file, and it causes |aWriter| to allocate
+  // over 200 KiB of memory.
+  jsonWriter->Start();
+  {
+    // Increment this number if the format changes.
+    jsonWriter->IntProperty("version", 1);
+    jsonWriter->BoolProperty("hasMozMallocUsableSize",
+                             mgr->GetHasMozMallocUsableSize());
+    jsonWriter->StartArrayProperty("reports");
+  }
+
+  RefPtr<HandleReportAndFinishReportingCallbacks>
+      handleReportAndFinishReporting =
+          new HandleReportAndFinishReportingCallbacks(
+              std::move(jsonWriter), aFinishDumping, aFinishDumpingData);
+  rv = mgr->GetReportsExtended(
+      handleReportAndFinishReporting, nullptr, handleReportAndFinishReporting,
+      nullptr, aAnonymize, aMinimizeMemoryUsage, aDMDIdentifier);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsMemoryInfoDumper::DumpMemoryReportsToNamedFile(
+    const nsAString& aFilename, nsIFinishDumpingCallback* aFinishDumping,
+    nsISupports* aFinishDumpingData, bool aAnonymize,
+    bool aMinimizeMemoryUsage) {
+  MOZ_ASSERT(!aFilename.IsEmpty());
+
+  // Create the file.
+
+  nsCOMPtr<nsIFile> reportsFile;
+  nsresult rv = NS_NewLocalFile(aFilename, false, getter_AddRefs(reportsFile));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  reportsFile->InitWithPath(aFilename);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool exists;
+  rv = reportsFile->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!exists) {
+    rv = reportsFile->Create(nsIFile::NORMAL_FILE_TYPE, 0644);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  nsString dmdIdent;
+  return DumpMemoryInfoToFile(reportsFile, aFinishDumping, aFinishDumpingData,
+                              aAnonymize, aMinimizeMemoryUsage, dmdIdent);
+}
+
+NS_IMETHODIMP
+nsMemoryInfoDumper::DumpMemoryInfoToTempDir(const nsAString& aIdentifier,
+                                            bool aAnonymize,
+                                            bool aMinimizeMemoryUsage) {
+  nsString identifier(aIdentifier);
+  EnsureNonEmptyIdentifier(identifier);
+
+  // Open a new file named something like
+  //
+  //   incomplete-memory-report-<identifier>-<pid>.json.gz
+  //
+  // in NS_OS_TEMP_DIR for writing.  When we're finished writing the report,
+  // we'll rename this file and get rid of the "incomplete-" prefix.
+  //
+  // We do this because we don't want scripts which poll the filesystem
+  // looking for memory report dumps to grab a file before we're finished
+  // writing to it.
+
+  // The "unified" indicates that we merge the memory reports from all
+  // processes and write out one file, rather than a separate file for
+  // each process as was the case before bug 946407.  This is so that
+  // the get_about_memory.py script in the B2G repository can
+  // determine when it's done waiting for files to appear.
+  nsCString reportsFinalFilename;
+  MakeFilename("unified-memory-report", identifier, getpid(), "json.gz",
+               reportsFinalFilename);
+
+  nsCOMPtr<nsIFile> reportsTmpFile;
+  nsresult rv;
+  // In Android case, this function will open a file named aFilename under
+  // specific folder (/data/local/tmp/memory-reports). Otherwise, it will
+  // open a file named aFilename under "NS_OS_TEMP_DIR".
+  rv = nsDumpUtils::OpenTempFile("incomplete-"_ns + reportsFinalFilename,
+                                 getter_AddRefs(reportsTmpFile),
+                                 "memory-reports"_ns);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  RefPtr<TempDirFinishCallback> finishDumping =
+      new TempDirFinishCallback(reportsTmpFile, reportsFinalFilename);
+
+  return DumpMemoryInfoToFile(reportsTmpFile, finishDumping, nullptr,
+                              aAnonymize, aMinimizeMemoryUsage, identifier);
+}
+
+#ifdef MOZ_DMD
+dmd::DMDFuncs::Singleton dmd::DMDFuncs::sSingleton;
+
+nsresult nsMemoryInfoDumper::OpenDMDFile(const nsAString& aIdentifier, int aPid,
+                                         FILE** aOutFile) {
+  if (!dmd::IsRunning()) {
+    *aOutFile = nullptr;
+    return NS_OK;
+  }
+
+  // Create a filename like dmd-<identifier>-<pid>.json.gz, which will be used
+  // if DMD is enabled.
+  nsCString dmdFilename;
+  MakeFilename("dmd", aIdentifier, aPid, "json.gz", dmdFilename);
+
+  // Open a new DMD file named |dmdFilename| in NS_OS_TEMP_DIR for writing,
+  // and dump DMD output to it.  This must occur after the memory reporters
+  // have been run (above), but before the memory-reports file has been
+  // renamed (so scripts can detect the DMD file, if present).
+
+  nsresult rv;
+  nsCOMPtr<nsIFile> dmdFile;
+  rv = nsDumpUtils::OpenTempFile(dmdFilename, getter_AddRefs(dmdFile),
+                                 "memory-reports"_ns);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  rv = dmdFile->OpenANSIFileDesc("wb", aOutFile);
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "OpenANSIFileDesc failed");
+
+  // Print the path, because on some platforms (e.g. Mac) it's not obvious.
+  dmd::StatusMsg("opened %s for writing\n", dmdFile->HumanReadablePath().get());
+
+  return rv;
+}
+
+nsresult nsMemoryInfoDumper::DumpDMDToFile(FILE* aFile) {
+  RefPtr<nsGZFileWriter> gzWriter = new nsGZFileWriter();
+  nsresult rv = gzWriter->InitANSIFileDesc(aFile);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // Dump DMD's memory reports analysis to the file.
+  dmd::Analyze(MakeUnique<GZWriterWrapper>(gzWriter));
+
+  rv = gzWriter->Finish();
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "Finish failed");
+  return rv;
+}
+#endif  // MOZ_DMD