Disallow throttling while running requestAnimationFrame callbacks

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

 /*
  * 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 111 matching lines @@
 
         ~DetachScope()
         {
             m_documentLifecycle.decrementDetachCount();
         }
 
     private:
         DocumentLifecycle& m_documentLifecycle;
     };
 
+    // Throttling is disabled by default. Instantiating this class allows
+    // throttling (e.g., during BeginMainFrame). If a script needs to run inside
+    // this scope, DisallowThrottlingScope should be used to let the script
+    // perform a synchronous layout if necessary.
     class CORE_EXPORT AllowThrottlingScope {
         STACK_ALLOCATED();
         WTF_MAKE_NONCOPYABLE(AllowThrottlingScope);
     public:
         AllowThrottlingScope(DocumentLifecycle&);
         ~AllowThrottlingScope();
     };
 
+    class CORE_EXPORT DisallowThrottlingScope {
+        STACK_ALLOCATED();
+        WTF_MAKE_NONCOPYABLE(DisallowThrottlingScope);
+
+    public:
+        DisallowThrottlingScope(DocumentLifecycle&);
+        ~DisallowThrottlingScope();
+
+    private:
+        int m_savedCount;
+    };
+
     DocumentLifecycle();
     ~DocumentLifecycle();
 
     bool isActive() const { return m_state > Inactive && m_state < Stopping; }
     LifecycleState state() const { return m_state; }
 
     bool stateAllowsTreeMutations() const;
     bool stateAllowsLayoutTreeMutations() const;
     bool stateAllowsDetach() const;
     bool stateAllowsLayoutInvalidation() const;
@@ skipping 65 matching lines @@
     return m_state != InPerformLayout
         && m_state != InCompositingUpdate
         && m_state != InPaintInvalidation
         && m_state != InUpdatePaintProperties
         && m_state != InPaint;
 }
 
 } // namespace blink
 
 #endif