diff -r 000000000000 -r 6474c204b198 dom/base/nsWindowMemoryReporter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/base/nsWindowMemoryReporter.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,247 @@
+/* -*- 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/. */
+
+#ifndef nsWindowMemoryReporter_h__
+#define nsWindowMemoryReporter_h__
+
+#include "nsIMemoryReporter.h"
+#include "nsIObserver.h"
+#include "nsITimer.h"
+#include "nsDataHashtable.h"
+#include "nsWeakReference.h"
+#include "nsAutoPtr.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/TimeStamp.h"
+#include "nsArenaMemoryStats.h"
+
+class nsWindowSizes {
+#define FOR_EACH_SIZE(macro) \
+  macro(DOM,   mDOMElementNodesSize) \
+  macro(DOM,   mDOMTextNodesSize) \
+  macro(DOM,   mDOMCDATANodesSize) \
+  macro(DOM,   mDOMCommentNodesSize) \
+  macro(DOM,   mDOMEventTargetsSize) \
+  macro(DOM,   mDOMOtherSize) \
+  macro(Style, mStyleSheetsSize) \
+  macro(Other, mLayoutPresShellSize) \
+  macro(Style, mLayoutStyleSetsSize) \
+  macro(Other, mLayoutTextRunsSize) \
+  macro(Other, mLayoutPresContextSize) \
+  macro(Other, mPropertyTablesSize) \
+
+public:
+  nsWindowSizes(mozilla::MallocSizeOf aMallocSizeOf)
+    :
+      #define ZERO_SIZE(kind, mSize)  mSize(0),
+      FOR_EACH_SIZE(ZERO_SIZE)
+      #undef ZERO_SIZE
+      mDOMEventTargetsCount(0),
+      mDOMEventListenersCount(0),
+      mArenaStats(),
+      mMallocSizeOf(aMallocSizeOf)
+  {}
+
+  void addToTabSizes(nsTabSizes *sizes) const {
+    #define ADD_TO_TAB_SIZES(kind, mSize) sizes->add(nsTabSizes::kind, mSize);
+    FOR_EACH_SIZE(ADD_TO_TAB_SIZES)
+    #undef ADD_TO_TAB_SIZES
+    mArenaStats.addToTabSizes(sizes);
+  }
+
+  #define DECL_SIZE(kind, mSize) size_t mSize;
+  FOR_EACH_SIZE(DECL_SIZE);
+  #undef DECL_SIZE
+
+  uint32_t mDOMEventTargetsCount;
+  uint32_t mDOMEventListenersCount;
+
+  nsArenaMemoryStats mArenaStats;
+  mozilla::MallocSizeOf mMallocSizeOf;
+
+#undef FOR_EACH_SIZE
+};
+
+/**
+ * nsWindowMemoryReporter is responsible for the 'explicit/window-objects'
+ * memory reporter.
+ *
+ * We classify DOM window objects into one of three categories:
+ *
+ *   - "active" windows, which are displayed in a tab (as the top-level window
+ *     or an iframe),
+ *
+ *   - "cached" windows, which are in the fastback cache (aka the bfcache), and
+ *
+ *   - "detached" windows, which have a null docshell.  A window becomes
+ *     detached when its <iframe> or tab containing the window is destroyed --
+ *     i.e., when the window is no longer active or cached.
+ *
+ * Additionally, we classify a subset of detached windows as "ghost" windows.
+ * Although ghost windows can happen legitimately (a page can hold a reference
+ * to a cross-domain window and then close its container), the presence of
+ * ghost windows is often indicative of a memory leak.
+ *
+ * A window is a ghost if it meets the following three criteria:
+ *
+ *   1) The window is detached.
+ *
+ *   2) There exist no non-detached windows with the same base domain as
+ *      the window's principal.  (For example, the base domain of
+ *      "wiki.mozilla.co.uk" is "mozilla.co.uk".)  This criterion makes us less
+ *      likely to flag a legitimately held-alive detached window as a ghost.
+ *
+ *   3) The window has met criteria (1) and (2) above for at least
+ *      memory.ghost_window_timeout_seconds.  This criterion is in place so we
+ *      don't immediately declare a window a ghost before the GC/CC has had a
+ *      chance to run.
+ *
+ * nsWindowMemoryReporter observes window detachment and uses mDetachedWindows
+ * to remember when a window first met criteria (1) and (2).  When we generate
+ * a memory report, we use this accounting to determine which windows are
+ * ghosts.
+ *
+ *
+ * We use the following memory reporter path for active and cached windows:
+ *
+ *   explicit/window-objects/top(<top-outer-uri>, id=<top-outer-id>)/<category>/window(<window-uri>)/...
+ *
+ * For detached and ghost windows, we use
+ *
+ *   explicit/window-objects/top(none)/<category>/window(<window-uri>)/...
+ *
+ * Where
+ *
+ * - <category> is "active", "cached", "detached", or "ghost", as described
+ *   above.
+ *
+ * - <top-outer-id> is the window id of the top outer window (i.e. the tab, or
+ *   the top level chrome window).  Exposing this ensures that each tab gets
+ *   its own sub-tree, even if multiple tabs are showing the same URI.
+ *
+ * - <top-uri> is the URI of the top window.  Excepting special windows (such
+ *   as browser.xul or hiddenWindow.html) it's what the address bar shows for
+ *   the tab.
+ *
+ */
+class nsWindowMemoryReporter MOZ_FINAL : public nsIMemoryReporter,
+                                         public nsIObserver,
+                                         public nsSupportsWeakReference
+{
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIMEMORYREPORTER
+  NS_DECL_NSIOBSERVER
+
+  static void Init();
+
+  ~nsWindowMemoryReporter();
+
+#ifdef DEBUG
+  /**
+   * Unlink all known ghost windows, to enable investigating what caused them
+   * to become ghost windows in the first place.
+   */
+  static void UnlinkGhostWindows();
+#endif
+
+private:
+  /**
+   * nsGhostWindowReporter generates the "ghost-windows" report, which counts
+   * the number of ghost windows present.
+   */
+  class GhostWindowsReporter MOZ_FINAL : public nsIMemoryReporter
+  {
+  public:
+    NS_DECL_ISUPPORTS
+
+    static int64_t DistinguishedAmount();
+
+    NS_IMETHOD
+    CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData)
+    {
+      return MOZ_COLLECT_REPORT(
+        "ghost-windows", KIND_OTHER, UNITS_COUNT, DistinguishedAmount(),
+"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, does not share a domain 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.");
+    }
+  };
+
+  // Protect ctor, use Init() instead.
+  nsWindowMemoryReporter();
+
+  /**
+   * Get the number of seconds for which a window must satisfy ghost criteria
+   * (1) and (2) before we deem that it satisfies criterion (3).
+   */
+  uint32_t GetGhostTimeout();
+
+  void ObserveDOMWindowDetached(nsISupports* aWindow);
+  void ObserveAfterMinimizeMemoryUsage();
+
+  /**
+   * Iterate over all weak window pointers in mDetachedWindows and update our
+   * accounting of which windows meet ghost criterion (2).
+   *
+   * This method also cleans up mDetachedWindows, removing entries for windows
+   * which have been destroyed or are no longer detached.
+   *
+   * If aOutGhostIDs is non-null, we populate it with the Window IDs of the
+   * ghost windows.
+   *
+   * This is called asynchronously after we observe a DOM window being detached
+   * from its docshell, and also right before we generate a memory report.
+   */
+  void CheckForGhostWindows(nsTHashtable<nsUint64HashKey> *aOutGhostIDs = nullptr);
+
+  /**
+   * Eventually do a check for ghost windows, if we haven't done one recently
+   * and we aren't already planning to do one soon.
+   */
+  void AsyncCheckForGhostWindows();
+
+  /**
+   * Kill the check timer, if it exists.
+   */
+  void KillCheckTimer();
+
+  static void CheckTimerFired(nsITimer* aTimer, void* aClosure);
+
+  /**
+   * Maps a weak reference to a detached window (nsIWeakReference) to the time
+   * when we observed that the window met ghost criterion (2) above.
+   *
+   * If the window has not yet met criterion (2) it maps to the null timestamp.
+   *
+   * (Although windows are not added to this table until they're detached, it's
+   * possible for a detached window to become non-detached, and we won't
+   * remove it from the table until CheckForGhostWindows runs.)
+   */
+  nsDataHashtable<nsISupportsHashKey, mozilla::TimeStamp> mDetachedWindows;
+
+  /**
+   * Track the last time we ran CheckForGhostWindows(), to avoid running it
+   * too often after a DOM window is detached.
+   */
+  mozilla::TimeStamp mLastCheckForGhostWindows;
+
+  nsCOMPtr<nsITimer> mCheckTimer;
+
+  bool mCycleCollectorIsRunning;
+
+  bool mCheckTimerWaitingForCCEnd;
+};
+
+#endif // nsWindowMemoryReporter_h__
+