Throttle rendering pipeline for invisible frames

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

Index: third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp
diff --git a/third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp b/third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp
index efc1b4b99a161bf0e73e1faf24b2430f7a210383..bb39efdae2d6593659b5ff44066ce543c4e09237 100644
--- a/third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp
+++ b/third_party/WebKit/Source/core/dom/DocumentLifecycle.cpp
@@ -38,6 +38,10 @@ 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)
@@ -62,6 +66,17 @@ 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)
@@ -291,6 +306,22 @@ void DocumentLifecycle::ensureStateAtMost(State 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