Throttle rendering pipeline for invisible frames

third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #include "config.h"
 #include "core/dom/DocumentLifecycle.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/Assertions.h"
 
 namespace blink {
 
 static DocumentLifecycle::DeprecatedTransition* s_deprecatedTransitionStack = 0;
 
+// TODO(skyostil): Come up with a better way to store cross-frame lifecycle
+// related data to avoid this being a global setting.
+static unsigned s_preventThrottlingCount = 0;
+
 DocumentLifecycle::Scope::Scope(DocumentLifecycle& lifecycle, State finalState)
     : m_lifecycle(lifecycle)
     , m_finalState(finalState)
 {
 }
 
 DocumentLifecycle::Scope::~Scope()
 {
     m_lifecycle.advanceTo(m_finalState);
 }
 
 DocumentLifecycle::DeprecatedTransition::DeprecatedTransition(State from, State to)
     : m_previous(s_deprecatedTransitionStack)
     , m_from(from)
     , m_to(to)
 {
     s_deprecatedTransitionStack = this;
 }
 
 DocumentLifecycle::DeprecatedTransition::~DeprecatedTransition()
 {
     s_deprecatedTransitionStack = m_previous;
 }
 
+DocumentLifecycle::PreventThrottlingScope::PreventThrottlingScope(DocumentLifecycle& lifecycle)
+    : m_lifecycle(lifecycle)
+{
+    m_lifecycle.incrementPreventThrottlingCount();

[esprehn, 2015/10/16 21:40:45]

if you're going to put these out of line you don't need the increment/decrement
methods, just access the s_preventThrottlingCount directly. DetachScope uses
methods because it's inline.

[Sami, 2015/10/19 10:51:06]

Ah, of course. Done.

+}
+
+DocumentLifecycle::PreventThrottlingScope::~PreventThrottlingScope()
+{
+    m_lifecycle.decrementPreventThrottlingCount();
+}
+
 DocumentLifecycle::DocumentLifecycle()
     : m_state(Uninitialized)
     , m_detachCount(0)
 {
 }
 
 DocumentLifecycle::~DocumentLifecycle()
 {
 }
 
@@ skipping 209 matching lines @@
 void DocumentLifecycle::ensureStateAtMost(State state)
 {
     ASSERT(state == VisualUpdatePending || state == StyleClean || state == LayoutClean);
     if (m_state <= state)
         return;
     ASSERT_WITH_MESSAGE(canRewindTo(state),
         "Cannot rewind document lifecycle from %s to %s.", stateAsDebugString(m_state), stateAsDebugString(state));
     m_state = state;
 }
 
+void DocumentLifecycle::incrementPreventThrottlingCount()
+{
+    s_preventThrottlingCount++;
+}
+
+void DocumentLifecycle::decrementPreventThrottlingCount()
+{
+    ASSERT(s_preventThrottlingCount > 0);
+    s_preventThrottlingCount--;
+}
+
+bool DocumentLifecycle::throttlingAllowed() const
+{
+    return !s_preventThrottlingCount;
+}
+
 #if ENABLE(ASSERT)
 #define DEBUG_STRING_CASE(StateName) \
     case StateName: return #StateName
 
 const char* DocumentLifecycle::stateAsDebugString(const State state)
 {
     switch (state) {
         DEBUG_STRING_CASE(Uninitialized);
         DEBUG_STRING_CASE(Inactive);
         DEBUG_STRING_CASE(VisualUpdatePending);
@@ skipping 19 matching lines @@
         DEBUG_STRING_CASE(Stopped);
         DEBUG_STRING_CASE(Disposed);
     }
 
     ASSERT_NOT_REACHED();
     return "Unknown";
 }
 #endif
 
 }