Adding upstream version 110.0.1.upstream/110.0.1upstream

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

1 files changed, 936 insertions, 0 deletions

diff --git a/dom/base/nsWindowMemoryReporter.cpp b/dom/base/nsWindowMemoryReporter.cpp
new file mode 100644
index 0000000000..5b9ceedc44
--- /dev/null
+++ b/dom/base/nsWindowMemoryReporter.cpp
@@ -0,0 +1,936 @@
+/* -*- 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 "nsWindowMemoryReporter.h"
+#include "nsWindowSizes.h"
+#include "nsGlobalWindow.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/ResultExtensions.h"
+#include "nsNetCID.h"
+#include "nsPrintfCString.h"
+#include "XPCJSMemoryReporter.h"
+#include "js/MemoryMetrics.h"
+#include "nsQueryObject.h"
+#include "nsServiceManagerUtils.h"
+#include "nsXULPrototypeCache.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+StaticRefPtr<nsWindowMemoryReporter> sWindowReporter;
+
+/**
+ * Don't trigger a ghost window check when a DOM window is detached if we've
+ * run it this recently.
+ */
+const int32_t kTimeBetweenChecks = 45; /* seconds */
+
+nsWindowMemoryReporter::nsWindowMemoryReporter()
+    : mLastCheckForGhostWindows(TimeStamp::NowLoRes()),
+      mCycleCollectorIsRunning(false),
+      mCheckTimerWaitingForCCEnd(false),
+      mGhostWindowCount(0) {}
+
+nsWindowMemoryReporter::~nsWindowMemoryReporter() { KillCheckTimer(); }
+
+NS_IMPL_ISUPPORTS(nsWindowMemoryReporter, nsIMemoryReporter, nsIObserver,
+                  nsISupportsWeakReference)
+
+static nsresult AddNonJSSizeOfWindowAndItsDescendents(
+    nsGlobalWindowOuter* aWindow, nsTabSizes* aSizes) {
+  // Measure the window.
+  SizeOfState state(moz_malloc_size_of);
+  nsWindowSizes windowSizes(state);
+  aWindow->AddSizeOfIncludingThis(windowSizes);
+
+  // Measure the inner window, if there is one.
+  nsGlobalWindowInner* inner = aWindow->GetCurrentInnerWindowInternal();
+  if (inner) {
+    inner->AddSizeOfIncludingThis(windowSizes);
+  }
+
+  windowSizes.addToTabSizes(aSizes);
+
+  BrowsingContext* bc = aWindow->GetBrowsingContext();
+  if (!bc) {
+    return NS_OK;
+  }
+
+  // Measure this window's descendents.
+  for (const auto& frame : bc->Children()) {
+    if (auto* childWin = nsGlobalWindowOuter::Cast(frame->GetDOMWindow())) {
+      MOZ_TRY(AddNonJSSizeOfWindowAndItsDescendents(childWin, aSizes));
+    }
+  }
+  return NS_OK;
+}
+
+static nsresult NonJSSizeOfTab(nsPIDOMWindowOuter* aWindow, size_t* aDomSize,
+                               size_t* aStyleSize, size_t* aOtherSize) {
+  nsGlobalWindowOuter* window = nsGlobalWindowOuter::Cast(aWindow);
+
+  nsTabSizes sizes;
+  nsresult rv = AddNonJSSizeOfWindowAndItsDescendents(window, &sizes);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  *aDomSize = sizes.mDom;
+  *aStyleSize = sizes.mStyle;
+  *aOtherSize = sizes.mOther;
+  return NS_OK;
+}
+
+/* static */
+void nsWindowMemoryReporter::Init() {
+  MOZ_ASSERT(!sWindowReporter);
+  sWindowReporter = new nsWindowMemoryReporter();
+  ClearOnShutdown(&sWindowReporter);
+  RegisterStrongMemoryReporter(sWindowReporter);
+  RegisterNonJSSizeOfTab(NonJSSizeOfTab);
+
+  nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+  if (os) {
+    os->AddObserver(sWindowReporter, "after-minimize-memory-usage",
+                    /* weakRef = */ true);
+    os->AddObserver(sWindowReporter, "cycle-collector-begin",
+                    /* weakRef = */ true);
+    os->AddObserver(sWindowReporter, "cycle-collector-end",
+                    /* weakRef = */ true);
+  }
+
+  RegisterGhostWindowsDistinguishedAmount(GhostWindowsDistinguishedAmount);
+}
+
+/* static */
+nsWindowMemoryReporter* nsWindowMemoryReporter::Get() {
+  return sWindowReporter;
+}
+
+static nsCString GetWindowURISpec(nsGlobalWindowInner* aWindow) {
+  NS_ENSURE_TRUE(aWindow, ""_ns);
+
+  nsCOMPtr<Document> doc = aWindow->GetExtantDoc();
+  if (doc) {
+    nsCOMPtr<nsIURI> uri;
+    uri = doc->GetDocumentURI();
+    return uri->GetSpecOrDefault();
+  }
+  nsCOMPtr<nsIScriptObjectPrincipal> scriptObjPrincipal =
+      do_QueryObject(aWindow);
+  NS_ENSURE_TRUE(scriptObjPrincipal, ""_ns);
+
+  // GetPrincipal() will print a warning if the window does not have an outer
+  // window, so check here for an outer window first.  This code is
+  // functionally correct if we leave out the GetOuterWindow() check, but we
+  // end up printing a lot of warnings during debug mochitests.
+  if (!aWindow->GetOuterWindow()) {
+    return ""_ns;
+  }
+  nsIPrincipal* principal = scriptObjPrincipal->GetPrincipal();
+  if (!principal) {
+    return ""_ns;
+  }
+  nsCString spec;
+  principal->GetAsciiSpec(spec);
+  return spec;
+}
+
+static void AppendWindowURI(nsGlobalWindowInner* aWindow, nsACString& aStr,
+                            bool aAnonymize) {
+  nsCString spec = GetWindowURISpec(aWindow);
+
+  if (spec.IsEmpty()) {
+    // If we're unable to find a URI, we're dealing with a chrome window with
+    // no document in it (or somesuch), so we call this a "system window".
+    aStr += "[system]"_ns;
+    return;
+  }
+  if (aAnonymize && !aWindow->IsChromeWindow()) {
+    aStr.AppendPrintf("<anonymized-%" PRIu64 ">", aWindow->WindowID());
+    return;
+  }
+  // A hack: replace forward slashes with '\\' so they aren't
+  // treated as path separators.  Users of the reporters
+  // (such as about:memory) have to undo this change.
+  spec.ReplaceChar('/', '\\');
+  aStr += spec;
+}
+
+MOZ_DEFINE_MALLOC_SIZE_OF(WindowsMallocSizeOf)
+
+// The key is the window ID.
+using WindowPaths = nsTHashMap<nsUint64HashKey, nsCString>;
+
+static void ReportAmount(const nsCString& aBasePath, const char* aPathTail,
+                         size_t aAmount, const nsCString& aDescription,
+                         uint32_t aKind, uint32_t aUnits,
+                         nsIHandleReportCallback* aHandleReport,
+                         nsISupports* aData) {
+  if (aAmount == 0) {
+    return;
+  }
+
+  nsAutoCString path(aBasePath);
+  path += aPathTail;
+
+  aHandleReport->Callback(""_ns, path, aKind, aUnits, aAmount, aDescription,
+                          aData);
+}
+
+static void ReportSize(const nsCString& aBasePath, const char* aPathTail,
+                       size_t aAmount, const nsCString& aDescription,
+                       nsIHandleReportCallback* aHandleReport,
+                       nsISupports* aData) {
+  ReportAmount(aBasePath, aPathTail, aAmount, aDescription,
+               nsIMemoryReporter::KIND_HEAP, nsIMemoryReporter::UNITS_BYTES,
+               aHandleReport, aData);
+}
+
+static void ReportCount(const nsCString& aBasePath, const char* aPathTail,
+                        size_t aAmount, const nsCString& aDescription,
+                        nsIHandleReportCallback* aHandleReport,
+                        nsISupports* aData) {
+  ReportAmount(aBasePath, aPathTail, aAmount, aDescription,
+               nsIMemoryReporter::KIND_OTHER, nsIMemoryReporter::UNITS_COUNT,
+               aHandleReport, aData);
+}
+
+static void ReportDOMSize(const nsCString& aBasePath,
+                          nsDOMSizes& aTotalDOMSizes,
+                          nsIHandleReportCallback* aHandleReport,
+                          nsISupports* aData, nsDOMSizes aDOMSizes) {
+#define REPORT_DOM_SIZE(_windowPath, _pathTail, _field, _desc) \
+  ReportSize(_windowPath, _pathTail, aDOMSizes._field,         \
+             nsLiteralCString(_desc), aHandleReport, aData);   \
+  aTotalDOMSizes._field += aDOMSizes._field;
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/element-nodes", mDOMElementNodesSize,
+                  "Memory used by the element nodes in a window's DOM.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/text-nodes", mDOMTextNodesSize,
+                  "Memory used by the text nodes in a window's DOM.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/cdata-nodes", mDOMCDATANodesSize,
+                  "Memory used by the CDATA nodes in a window's DOM.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/comment-nodes", mDOMCommentNodesSize,
+                  "Memory used by the comment nodes in a window's DOM.");
+
+  REPORT_DOM_SIZE(
+      aBasePath, "/dom/event-targets", mDOMEventTargetsSize,
+      "Memory used by the event targets table in a window's DOM, and "
+      "the objects it points to, which include XHRs.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/performance/user-entries",
+                  mDOMPerformanceUserEntries,
+                  "Memory used for performance user entries.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/performance/resource-entries",
+                  mDOMPerformanceResourceEntries,
+                  "Memory used for performance resource entries.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/media-query-lists", mDOMMediaQueryLists,
+                  "Memory used by MediaQueryList objects for the window's "
+                  "document.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/resize-observers",
+                  mDOMResizeObserverControllerSize,
+                  "Memory used for resize observers.");
+
+  REPORT_DOM_SIZE(aBasePath, "/dom/other", mDOMOtherSize,
+                  "Memory used by a window's DOM that isn't measured by the "
+                  "other 'dom/' numbers.");
+#undef REPORT_DOM_SIZE
+}
+
+static void CollectWindowReports(nsGlobalWindowInner* aWindow,
+                                 nsWindowSizes* aWindowTotalSizes,
+                                 nsTHashSet<uint64_t>* aGhostWindowIDs,
+                                 WindowPaths* aWindowPaths,
+                                 WindowPaths* aTopWindowPaths,
+                                 nsIHandleReportCallback* aHandleReport,
+                                 nsISupports* aData, bool aAnonymize) {
+  nsAutoCString windowPath("explicit/");
+
+  // Avoid calling aWindow->GetInProcessTop() if there's no outer window.  It
+  // will work just fine, but will spew a lot of warnings.
+  nsGlobalWindowOuter* top = nullptr;
+  if (aWindow->GetOuterWindow()) {
+    // Our window should have a null top iff it has a null docshell.
+    MOZ_ASSERT(!!aWindow->GetInProcessTopInternal() ==
+               !!aWindow->GetDocShell());
+    top = aWindow->GetInProcessTopInternal();
+  }
+
+  windowPath += "window-objects/"_ns;
+
+  if (top) {
+    windowPath += "top("_ns;
+    AppendWindowURI(top->GetCurrentInnerWindowInternal(), windowPath,
+                    aAnonymize);
+    windowPath.AppendPrintf(", id=%" PRIu64 ")", top->WindowID());
+
+    aTopWindowPaths->InsertOrUpdate(aWindow->WindowID(), windowPath);
+
+    windowPath += aWindow->IsFrozen() ? "/cached/"_ns : "/active/"_ns;
+  } else {
+    if (aGhostWindowIDs->Contains(aWindow->WindowID())) {
+      windowPath += "top(none)/ghost/"_ns;
+    } else {
+      windowPath += "top(none)/detached/"_ns;
+    }
+  }
+
+  windowPath += "window("_ns;
+  AppendWindowURI(aWindow, windowPath, aAnonymize);
+  windowPath += ")"_ns;
+
+  // Use |windowPath|, but replace "explicit/" with "event-counts/".
+  nsCString censusWindowPath(windowPath);
+  censusWindowPath.ReplaceLiteral(0, strlen("explicit"), "event-counts");
+
+  // Remember the path for later.
+  aWindowPaths->InsertOrUpdate(aWindow->WindowID(), windowPath);
+
+// Report the size from windowSizes and add to the appropriate total in
+// aWindowTotalSizes.
+#define REPORT_SIZE(_pathTail, _field, _desc)                \
+  ReportSize(windowPath, _pathTail, windowSizes._field,      \
+             nsLiteralCString(_desc), aHandleReport, aData); \
+  aWindowTotalSizes->_field += windowSizes._field;
+
+// Report the size, which is a sum of other sizes, and so doesn't require
+// updating aWindowTotalSizes.
+#define REPORT_SUM_SIZE(_pathTail, _amount, _desc)                    \
+  ReportSize(windowPath, _pathTail, _amount, nsLiteralCString(_desc), \
+             aHandleReport, aData);
+
+// Like REPORT_SIZE, but for a count.
+#define REPORT_COUNT(_pathTail, _field, _desc)                 \
+  ReportCount(censusWindowPath, _pathTail, windowSizes._field, \
+              nsLiteralCString(_desc), aHandleReport, aData);  \
+  aWindowTotalSizes->_field += windowSizes._field;
+
+  // This SizeOfState contains the SeenPtrs used for all memory reporting of
+  // this window.
+  SizeOfState state(WindowsMallocSizeOf);
+  nsWindowSizes windowSizes(state);
+  aWindow->AddSizeOfIncludingThis(windowSizes);
+
+  ReportDOMSize(windowPath, aWindowTotalSizes->mDOMSizes, aHandleReport, aData,
+                windowSizes.mDOMSizes);
+
+  nsCString dataDocumentPath(windowPath);
+  dataDocumentPath += "/data-documents";
+  nsWindowSizes dataDocumentSizes(state);
+  aWindow->CollectDOMSizesForDataDocuments(dataDocumentSizes);
+  ReportDOMSize(dataDocumentPath, aWindowTotalSizes->mDOMSizes, aHandleReport,
+                aData, dataDocumentSizes.mDOMSizes);
+
+  REPORT_SIZE("/layout/style-sheets", mLayoutStyleSheetsSize,
+              "Memory used by document style sheets within a window.");
+
+  REPORT_SIZE("/layout/svg-mapped-declarations", mLayoutSvgMappedDeclarations,
+              "Memory used by mapped declarations of SVG elements");
+
+  REPORT_SIZE("/layout/shadow-dom/style-sheets",
+              mLayoutShadowDomStyleSheetsSize,
+              "Memory used by Shadow DOM style sheets within a window.");
+
+  // TODO(emilio): We might want to split this up between invalidation map /
+  // element-and-pseudos / revalidation too just like the style set.
+  REPORT_SIZE("/layout/shadow-dom/author-styles", mLayoutShadowDomAuthorStyles,
+              "Memory used by Shadow DOM computed rule data within a window.");
+
+  REPORT_SIZE("/layout/pres-shell", mLayoutPresShellSize,
+              "Memory used by layout's PresShell, along with any structures "
+              "allocated in its arena and not measured elsewhere, "
+              "within a window.");
+
+  REPORT_SIZE("/layout/display-list", mLayoutRetainedDisplayListSize,
+              "Memory used by the retained display list data, "
+              "along with any structures allocated in its arena and not "
+              "measured elsewhere, within a window.");
+
+  REPORT_SIZE("/layout/style-sets/stylist/rule-tree",
+              mLayoutStyleSetsStylistRuleTree,
+              "Memory used by rule trees within style sets within a window.");
+
+  REPORT_SIZE("/layout/style-sets/stylist/element-and-pseudos-maps",
+              mLayoutStyleSetsStylistElementAndPseudosMaps,
+              "Memory used by element and pseudos maps within style "
+              "sets within a window.");
+
+  REPORT_SIZE("/layout/style-sets/stylist/invalidation-map",
+              mLayoutStyleSetsStylistInvalidationMap,
+              "Memory used by invalidation maps within style sets "
+              "within a window.");
+
+  REPORT_SIZE("/layout/style-sets/stylist/revalidation-selectors",
+              mLayoutStyleSetsStylistRevalidationSelectors,
+              "Memory used by selectors for cache revalidation within "
+              "style sets within a window.");
+
+  REPORT_SIZE("/layout/style-sets/stylist/other", mLayoutStyleSetsStylistOther,
+              "Memory used by other Stylist data within style sets "
+              "within a window.");
+
+  REPORT_SIZE("/layout/style-sets/other", mLayoutStyleSetsOther,
+              "Memory used by other parts of style sets within a window.");
+
+  REPORT_SIZE("/layout/element-data-objects", mLayoutElementDataObjects,
+              "Memory used for ElementData objects, but not the things "
+              "hanging off them.");
+
+  REPORT_SIZE("/layout/text-runs", mLayoutTextRunsSize,
+              "Memory used for text-runs (glyph layout) in the PresShell's "
+              "frame tree, within a window.");
+
+  REPORT_SIZE("/layout/pres-contexts", mLayoutPresContextSize,
+              "Memory used for the PresContext in the PresShell's frame "
+              "within a window.");
+
+  REPORT_SIZE("/layout/frame-properties", mLayoutFramePropertiesSize,
+              "Memory used for frame properties attached to frames "
+              "within a window.");
+
+  REPORT_SIZE("/layout/computed-values/dom", mLayoutComputedValuesDom,
+              "Memory used by ComputedValues objects accessible from DOM "
+              "elements.");
+
+  REPORT_SIZE("/layout/computed-values/non-dom", mLayoutComputedValuesNonDom,
+              "Memory used by ComputedValues objects not accessible from DOM "
+              "elements.");
+
+  REPORT_SIZE("/layout/computed-values/visited", mLayoutComputedValuesVisited,
+              "Memory used by ComputedValues objects used for visited styles.");
+
+  REPORT_SIZE("/property-tables", mPropertyTablesSize,
+              "Memory used for the property tables within a window.");
+
+  REPORT_SIZE("/bindings", mBindingsSize,
+              "Memory used by bindings within a window.");
+
+  REPORT_COUNT("/dom/event-targets", mDOMEventTargetsCount,
+               "Number of non-node event targets in the event targets table "
+               "in a window's DOM, such as XHRs.");
+
+  REPORT_COUNT("/dom/event-listeners", mDOMEventListenersCount,
+               "Number of event listeners in a window, including event "
+               "listeners on nodes and other event targets.");
+
+  // There are many different kinds of frames, but it is very likely
+  // that only a few matter.  Implement a cutoff so we don't bloat
+  // about:memory with many uninteresting entries.
+  const size_t ARENA_SUNDRIES_THRESHOLD =
+      js::MemoryReportingSundriesThreshold();
+
+  size_t presArenaSundriesSize = 0;
+#define ARENA_OBJECT(name_, sundries_size_, prefix_)                    \
+  {                                                                     \
+    size_t size = windowSizes.mArenaSizes.NS_ARENA_SIZES_FIELD(name_);  \
+    if (size < ARENA_SUNDRIES_THRESHOLD) {                              \
+      sundries_size_ += size;                                           \
+    } else {                                                            \
+      REPORT_SUM_SIZE(prefix_ #name_, size,                             \
+                      "Memory used by objects of type " #name_          \
+                      " within a window.");                             \
+    }                                                                   \
+    aWindowTotalSizes->mArenaSizes.NS_ARENA_SIZES_FIELD(name_) += size; \
+  }
+#define PRES_ARENA_OBJECT(name_) \
+  ARENA_OBJECT(name_, presArenaSundriesSize, "/layout/pres-arena/")
+#include "nsPresArenaObjectList.h"
+#undef PRES_ARENA_OBJECT
+
+  if (presArenaSundriesSize > 0) {
+    REPORT_SUM_SIZE(
+        "/layout/pres-arena/sundries", presArenaSundriesSize,
+        "The sum of all memory used by objects in the arena which were too "
+        "small to be shown individually.");
+  }
+
+  size_t displayListArenaSundriesSize = 0;
+#define DISPLAY_LIST_ARENA_OBJECT(name_)            \
+  ARENA_OBJECT(name_, displayListArenaSundriesSize, \
+               "/layout/display-list-arena/")
+#include "nsDisplayListArenaTypes.h"
+#undef DISPLAY_LIST_ARENA_OBJECT
+
+  if (displayListArenaSundriesSize > 0) {
+    REPORT_SUM_SIZE(
+        "/layout/display-list-arena/sundries", displayListArenaSundriesSize,
+        "The sum of all memory used by objects in the DL arena which were too "
+        "small to be shown individually.");
+  }
+
+#undef ARENA_OBJECT
+
+  // There are many different kinds of style structs, but it is likely that
+  // only a few matter. Implement a cutoff so we don't bloat about:memory with
+  // many uninteresting entries.
+  const size_t STYLE_SUNDRIES_THRESHOLD =
+      js::MemoryReportingSundriesThreshold();
+
+  size_t styleSundriesSize = 0;
+#define STYLE_STRUCT(name_)                                             \
+  {                                                                     \
+    size_t size = windowSizes.mStyleSizes.NS_STYLE_SIZES_FIELD(name_);  \
+    if (size < STYLE_SUNDRIES_THRESHOLD) {                              \
+      styleSundriesSize += size;                                        \
+    } else {                                                            \
+      REPORT_SUM_SIZE("/layout/style-structs/" #name_, size,            \
+                      "Memory used by the " #name_                      \
+                      " style structs within a window.");               \
+    }                                                                   \
+    aWindowTotalSizes->mStyleSizes.NS_STYLE_SIZES_FIELD(name_) += size; \
+  }
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+
+  if (styleSundriesSize > 0) {
+    REPORT_SUM_SIZE(
+        "/layout/style-structs/sundries", styleSundriesSize,
+        "The sum of all memory used by style structs which were too "
+        "small to be shown individually.");
+  }
+
+#undef REPORT_SIZE
+#undef REPORT_SUM_SIZE
+#undef REPORT_COUNT
+}
+
+using WindowArray = nsTArray<RefPtr<nsGlobalWindowInner>>;
+
+NS_IMETHODIMP
+nsWindowMemoryReporter::CollectReports(nsIHandleReportCallback* aHandleReport,
+                                       nsISupports* aData, bool aAnonymize) {
+  nsGlobalWindowInner::InnerWindowByIdTable* windowsById =
+      nsGlobalWindowInner::GetWindowsTable();
+  NS_ENSURE_TRUE(windowsById, NS_OK);
+
+  // Hold on to every window in memory so that window objects can't be
+  // destroyed while we're calling the memory reporter callback.
+  const auto windows = ToTArray<WindowArray>(windowsById->Values());
+
+  // Get the IDs of all the "ghost" windows, and call
+  // aHandleReport->Callback() for each one.
+  nsTHashSet<uint64_t> ghostWindows;
+  CheckForGhostWindows(&ghostWindows);
+
+  for (const auto& key : ghostWindows) {
+    nsGlobalWindowInner* window = windowsById->Get(key);
+    if (!window) {
+      NS_WARNING("Could not look up window?");
+      continue;
+    }
+
+    nsAutoCString path;
+    path.AppendLiteral("ghost-windows/");
+    AppendWindowURI(window, path, aAnonymize);
+
+    aHandleReport->Callback(
+        /* process = */ ""_ns, path, nsIMemoryReporter::KIND_OTHER,
+        nsIMemoryReporter::UNITS_COUNT,
+        /* amount = */ 1,
+        /* description = */ "A ghost window."_ns, aData);
+  }
+
+  // clang-format off
+  MOZ_COLLECT_REPORT(
+    "ghost-windows", KIND_OTHER, UNITS_COUNT, ghostWindows.Count(),
+"The number of ghost windows present (the number of nodes underneath "
+"explicit/window-objects/top(none)/ghost, modulo race conditions).  A ghost "
+"window is not shown in any tab, is not in a browsing context group with any "
+"non-detached windows, and has met these criteria for at least "
+"memory.ghost_window_timeout_seconds, or has survived a round of "
+"about:memory's minimize memory usage button.\n\n"
+"Ghost windows can happen legitimately, but they are often indicative of "
+"leaks in the browser or add-ons.");
+  // clang-format on
+
+  WindowPaths windowPaths;
+  WindowPaths topWindowPaths;
+
+  // Collect window memory usage.
+  SizeOfState fakeState(nullptr);  // this won't be used
+  nsWindowSizes windowTotalSizes(fakeState);
+  for (uint32_t i = 0; i < windows.Length(); i++) {
+    CollectWindowReports(windows[i], &windowTotalSizes, &ghostWindows,
+                         &windowPaths, &topWindowPaths, aHandleReport, aData,
+                         aAnonymize);
+  }
+
+  // Report JS memory usage.  We do this from here because the JS memory
+  // reporter needs to be passed |windowPaths|.
+  xpc::JSReporter::CollectReports(&windowPaths, &topWindowPaths, aHandleReport,
+                                  aData, aAnonymize);
+
+  nsXULPrototypeCache::CollectMemoryReports(aHandleReport, aData);
+
+#define REPORT(_path, _amount, _desc)                                    \
+  aHandleReport->Callback(""_ns, nsLiteralCString(_path), KIND_OTHER,    \
+                          UNITS_BYTES, _amount, nsLiteralCString(_desc), \
+                          aData);
+
+  REPORT("window-objects/dom/element-nodes",
+         windowTotalSizes.mDOMSizes.mDOMElementNodesSize,
+         "This is the sum of all windows' 'dom/element-nodes' numbers.");
+
+  REPORT("window-objects/dom/text-nodes",
+         windowTotalSizes.mDOMSizes.mDOMTextNodesSize,
+         "This is the sum of all windows' 'dom/text-nodes' numbers.");
+
+  REPORT("window-objects/dom/cdata-nodes",
+         windowTotalSizes.mDOMSizes.mDOMCDATANodesSize,
+         "This is the sum of all windows' 'dom/cdata-nodes' numbers.");
+
+  REPORT("window-objects/dom/comment-nodes",
+         windowTotalSizes.mDOMSizes.mDOMCommentNodesSize,
+         "This is the sum of all windows' 'dom/comment-nodes' numbers.");
+
+  REPORT("window-objects/dom/event-targets",
+         windowTotalSizes.mDOMSizes.mDOMEventTargetsSize,
+         "This is the sum of all windows' 'dom/event-targets' numbers.");
+
+  REPORT("window-objects/dom/performance",
+         windowTotalSizes.mDOMSizes.mDOMPerformanceUserEntries +
+             windowTotalSizes.mDOMSizes.mDOMPerformanceResourceEntries,
+         "This is the sum of all windows' 'dom/performance/' numbers.");
+
+  REPORT("window-objects/dom/other", windowTotalSizes.mDOMSizes.mDOMOtherSize,
+         "This is the sum of all windows' 'dom/other' numbers.");
+
+  REPORT("window-objects/layout/style-sheets",
+         windowTotalSizes.mLayoutStyleSheetsSize,
+         "This is the sum of all windows' 'layout/style-sheets' numbers.");
+
+  REPORT("window-objects/layout/pres-shell",
+         windowTotalSizes.mLayoutPresShellSize,
+         "This is the sum of all windows' 'layout/arenas' numbers.");
+
+  REPORT("window-objects/layout/style-sets",
+         windowTotalSizes.mLayoutStyleSetsStylistRuleTree +
+             windowTotalSizes.mLayoutStyleSetsStylistElementAndPseudosMaps +
+             windowTotalSizes.mLayoutStyleSetsStylistInvalidationMap +
+             windowTotalSizes.mLayoutStyleSetsStylistRevalidationSelectors +
+             windowTotalSizes.mLayoutStyleSetsStylistOther +
+             windowTotalSizes.mLayoutStyleSetsOther,
+         "This is the sum of all windows' 'layout/style-sets/' numbers.");
+
+  REPORT("window-objects/layout/element-data-objects",
+         windowTotalSizes.mLayoutElementDataObjects,
+         "This is the sum of all windows' 'layout/element-data-objects' "
+         "numbers.");
+
+  REPORT("window-objects/layout/text-runs",
+         windowTotalSizes.mLayoutTextRunsSize,
+         "This is the sum of all windows' 'layout/text-runs' numbers.");
+
+  REPORT("window-objects/layout/pres-contexts",
+         windowTotalSizes.mLayoutPresContextSize,
+         "This is the sum of all windows' 'layout/pres-contexts' numbers.");
+
+  REPORT("window-objects/layout/frame-properties",
+         windowTotalSizes.mLayoutFramePropertiesSize,
+         "This is the sum of all windows' 'layout/frame-properties' numbers.");
+
+  REPORT("window-objects/layout/computed-values",
+         windowTotalSizes.mLayoutComputedValuesDom +
+             windowTotalSizes.mLayoutComputedValuesNonDom +
+             windowTotalSizes.mLayoutComputedValuesVisited,
+         "This is the sum of all windows' 'layout/computed-values/' numbers.");
+
+  REPORT("window-objects/property-tables", windowTotalSizes.mPropertyTablesSize,
+         "This is the sum of all windows' 'property-tables' numbers.");
+
+  size_t presArenaTotal = 0;
+#define PRES_ARENA_OBJECT(name_) \
+  presArenaTotal += windowTotalSizes.mArenaSizes.NS_ARENA_SIZES_FIELD(name_);
+#include "nsPresArenaObjectList.h"
+#undef PRES_ARENA_OBJECT
+
+  REPORT("window-objects/layout/pres-arena", presArenaTotal,
+         "Memory used for the pres arena within windows. "
+         "This is the sum of all windows' 'layout/pres-arena/' numbers.");
+
+  size_t displayListArenaTotal = 0;
+#define DISPLAY_LIST_ARENA_OBJECT(name_) \
+  displayListArenaTotal +=               \
+      windowTotalSizes.mArenaSizes.NS_ARENA_SIZES_FIELD(name_);
+#include "nsDisplayListArenaTypes.h"
+#undef DISPLAY_LIST_ARENA_OBJECT
+
+  REPORT("window-objects/layout/display-list-arena", displayListArenaTotal,
+         "Memory used for the display list arena within windows. This is the "
+         "sum of all windows' 'layout/display-list-arena/' numbers.");
+
+  size_t styleTotal = 0;
+#define STYLE_STRUCT(name_) \
+  styleTotal += windowTotalSizes.mStyleSizes.NS_STYLE_SIZES_FIELD(name_);
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
+
+  REPORT("window-objects/layout/style-structs", styleTotal,
+         "Memory used for style structs within windows. This is the sum of "
+         "all windows' 'layout/style-structs/' numbers.");
+
+#undef REPORT
+
+  return NS_OK;
+}
+
+uint32_t nsWindowMemoryReporter::GetGhostTimeout() {
+  return Preferences::GetUint("memory.ghost_window_timeout_seconds", 60);
+}
+
+NS_IMETHODIMP
+nsWindowMemoryReporter::Observe(nsISupports* aSubject, const char* aTopic,
+                                const char16_t* aData) {
+  if (!strcmp(aTopic, "after-minimize-memory-usage")) {
+    ObserveAfterMinimizeMemoryUsage();
+  } else if (!strcmp(aTopic, "cycle-collector-begin")) {
+    if (mCheckTimer) {
+      mCheckTimerWaitingForCCEnd = true;
+      KillCheckTimer();
+    }
+    mCycleCollectorIsRunning = true;
+  } else if (!strcmp(aTopic, "cycle-collector-end")) {
+    mCycleCollectorIsRunning = false;
+    if (mCheckTimerWaitingForCCEnd) {
+      mCheckTimerWaitingForCCEnd = false;
+      AsyncCheckForGhostWindows();
+    }
+  } else {
+    MOZ_ASSERT(false);
+  }
+
+  return NS_OK;
+}
+
+void nsWindowMemoryReporter::ObserveDOMWindowDetached(
+    nsGlobalWindowInner* aWindow) {
+  nsWeakPtr weakWindow = do_GetWeakReference(aWindow);
+  if (!weakWindow) {
+    NS_WARNING("Couldn't take weak reference to a window?");
+    return;
+  }
+
+  mDetachedWindows.InsertOrUpdate(weakWindow, TimeStamp());
+
+  AsyncCheckForGhostWindows();
+}
+
+// static
+void nsWindowMemoryReporter::CheckTimerFired(nsITimer* aTimer, void* aData) {
+  if (sWindowReporter) {
+    MOZ_ASSERT(!sWindowReporter->mCycleCollectorIsRunning);
+    sWindowReporter->CheckForGhostWindows();
+  }
+}
+
+void nsWindowMemoryReporter::AsyncCheckForGhostWindows() {
+  if (mCheckTimer) {
+    return;
+  }
+
+  if (mCycleCollectorIsRunning) {
+    mCheckTimerWaitingForCCEnd = true;
+    return;
+  }
+
+  // If more than kTimeBetweenChecks seconds have elapsed since the last check,
+  // timerDelay is 0.  Otherwise, it is kTimeBetweenChecks, reduced by the time
+  // since the last check.  Reducing the delay by the time since the last check
+  // prevents the timer from being completely starved if it is repeatedly killed
+  // and restarted.
+  int32_t timeSinceLastCheck =
+      (TimeStamp::NowLoRes() - mLastCheckForGhostWindows).ToSeconds();
+  int32_t timerDelay =
+      (kTimeBetweenChecks - std::min(timeSinceLastCheck, kTimeBetweenChecks)) *
+      PR_MSEC_PER_SEC;
+
+  NS_NewTimerWithFuncCallback(
+      getter_AddRefs(mCheckTimer), CheckTimerFired, nullptr, timerDelay,
+      nsITimer::TYPE_ONE_SHOT,
+      "nsWindowMemoryReporter::AsyncCheckForGhostWindows_timer");
+}
+
+void nsWindowMemoryReporter::ObserveAfterMinimizeMemoryUsage() {
+  // Someone claims they've done enough GC/CCs so that all eligible windows
+  // have been free'd.  So we deem that any windows which satisfy ghost
+  // criteria (1) and (2) now satisfy criterion (3) as well.
+  //
+  // To effect this change, we'll backdate some of our timestamps.
+
+  TimeStamp minTimeStamp =
+      TimeStamp::Now() - TimeDuration::FromSeconds(GetGhostTimeout());
+
+  for (auto iter = mDetachedWindows.Iter(); !iter.Done(); iter.Next()) {
+    TimeStamp& timeStamp = iter.Data();
+    if (!timeStamp.IsNull() && timeStamp > minTimeStamp) {
+      timeStamp = minTimeStamp;
+    }
+  }
+}
+
+/**
+ * Iterate over mDetachedWindows and update it to reflect the current state of
+ * the world.  In particular:
+ *
+ *   - Remove weak refs to windows which no longer exist.
+ *
+ *   - Remove references to windows which are no longer detached.
+ *
+ *   - Reset the timestamp on detached windows which share a domain with a
+ *     non-detached window (they no longer meet ghost criterion (2)).
+ *
+ *   - If a window now meets ghost criterion (2) but didn't before, set its
+ *     timestamp to now.
+ *
+ * Additionally, if aOutGhostIDs is not null, fill it with the window IDs of
+ * all ghost windows we found.
+ */
+void nsWindowMemoryReporter::CheckForGhostWindows(
+    nsTHashSet<uint64_t>* aOutGhostIDs /* = nullptr */) {
+  nsGlobalWindowInner::InnerWindowByIdTable* windowsById =
+      nsGlobalWindowInner::GetWindowsTable();
+  if (!windowsById) {
+    NS_WARNING("GetWindowsTable returned null");
+    return;
+  }
+
+  mLastCheckForGhostWindows = TimeStamp::NowLoRes();
+  KillCheckTimer();
+
+  nsTHashSet<BrowsingContextGroup*> nonDetachedBrowsingContextGroups;
+
+  // Populate nonDetachedBrowsingContextGroups.
+  for (const auto& entry : *windowsById) {
+    // Null outer window implies null top, but calling GetInProcessTop() when
+    // there's no outer window causes us to spew debug warnings.
+    nsGlobalWindowInner* window = entry.GetWeak();
+    if (!window->GetOuterWindow() || !window->GetInProcessTopInternal() ||
+        !window->GetBrowsingContextGroup()) {
+      // This window is detached, so we don't care about its browsing
+      // context group.
+      continue;
+    }
+
+    nonDetachedBrowsingContextGroups.Insert(window->GetBrowsingContextGroup());
+  }
+
+  // Update mDetachedWindows and write the ghost window IDs into aOutGhostIDs,
+  // if it's not null.
+  uint32_t ghostTimeout = GetGhostTimeout();
+  TimeStamp now = mLastCheckForGhostWindows;
+  mGhostWindowCount = 0;
+  for (auto iter = mDetachedWindows.Iter(); !iter.Done(); iter.Next()) {
+    nsWeakPtr weakKey = do_QueryInterface(iter.Key());
+    nsCOMPtr<mozIDOMWindow> iwindow = do_QueryReferent(weakKey);
+    if (!iwindow) {
+      // The window object has been destroyed.  Stop tracking its weak ref in
+      // our hashtable.
+      iter.Remove();
+      continue;
+    }
+
+    nsPIDOMWindowInner* window = nsPIDOMWindowInner::From(iwindow);
+
+    // Avoid calling GetInProcessTop() if we have no outer window.  Nothing
+    // will break if we do, but it will spew debug output, which can cause our
+    // test logs to overflow.
+    nsCOMPtr<nsPIDOMWindowOuter> top;
+    if (window->GetOuterWindow()) {
+      top = window->GetOuterWindow()->GetInProcessTop();
+    }
+
+    if (top) {
+      // The window is no longer detached, so we no longer want to track it.
+      iter.Remove();
+      continue;
+    }
+
+    TimeStamp& timeStamp = iter.Data();
+    BrowsingContextGroup* browsingContextGroup =
+        window->GetBrowsingContextGroup();
+    if (browsingContextGroup &&
+        nonDetachedBrowsingContextGroups.Contains(browsingContextGroup)) {
+      // This window is in the same browsing context group as a non-detached
+      // window, so reset its clock.
+      timeStamp = TimeStamp();
+    } else {
+      // This window is not in the same browsing context group as a non-detached
+      // window, so it meets ghost criterion (2).
+      if (timeStamp.IsNull()) {
+        // This may become a ghost window later; start its clock.
+        timeStamp = now;
+      } else if ((now - timeStamp).ToSeconds() > ghostTimeout) {
+        // This definitely is a ghost window, so add it to aOutGhostIDs, if
+        // that is not null.
+        mGhostWindowCount++;
+        if (aOutGhostIDs && window) {
+          aOutGhostIDs->Insert(window->WindowID());
+        }
+      }
+    }
+  }
+
+  Telemetry::ScalarSetMaximum(
+      Telemetry::ScalarID::MEMORYREPORTER_MAX_GHOST_WINDOWS, mGhostWindowCount);
+}
+
+/* static */
+int64_t nsWindowMemoryReporter::GhostWindowsDistinguishedAmount() {
+  return sWindowReporter->mGhostWindowCount;
+}
+
+void nsWindowMemoryReporter::KillCheckTimer() {
+  if (mCheckTimer) {
+    mCheckTimer->Cancel();
+    mCheckTimer = nullptr;
+  }
+}
+
+#ifdef DEBUG
+/* static */
+void nsWindowMemoryReporter::UnlinkGhostWindows() {
+  if (!sWindowReporter) {
+    return;
+  }
+
+  nsGlobalWindowInner::InnerWindowByIdTable* windowsById =
+      nsGlobalWindowInner::GetWindowsTable();
+  if (!windowsById) {
+    return;
+  }
+
+  // Hold on to every window in memory so that window objects can't be
+  // destroyed while we're calling the UnlinkGhostWindows callback.
+  const auto windows = ToTArray<WindowArray>(windowsById->Values());
+
+  // Get the IDs of all the "ghost" windows, and unlink them all.
+  nsTHashSet<uint64_t> ghostWindows;
+  sWindowReporter->CheckForGhostWindows(&ghostWindows);
+  for (const auto& key : ghostWindows) {
+    nsGlobalWindowInner::InnerWindowByIdTable* windowsById =
+        nsGlobalWindowInner::GetWindowsTable();
+    if (!windowsById) {
+      continue;
+    }
+
+    RefPtr<nsGlobalWindowInner> window = windowsById->Get(key);
+    if (window) {
+      window->RiskyUnlink();
+    }
+  }
+}
+#endif