Disallow throttling while running requestAnimationFrame callbacks

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

Index: third_party/WebKit/Source/core/dom/DocumentLifecycle.h
diff --git a/third_party/WebKit/Source/core/dom/DocumentLifecycle.h b/third_party/WebKit/Source/core/dom/DocumentLifecycle.h
index 6a2d1f062b5f4a44091d1b2a095fd74c25714231..b744be68a65bcca8d90c00c4d72e2ee6d54a0ae0 100644
--- a/third_party/WebKit/Source/core/dom/DocumentLifecycle.h
+++ b/third_party/WebKit/Source/core/dom/DocumentLifecycle.h
@@ -129,6 +129,10 @@ public:
         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);
@@ -137,6 +141,18 @@ public:
         ~AllowThrottlingScope();
     };
 
+    class CORE_EXPORT DisallowThrottlingScope {
+        STACK_ALLOCATED();
+        WTF_MAKE_NONCOPYABLE(DisallowThrottlingScope);
+
+    public:
+        DisallowThrottlingScope(DocumentLifecycle&);
+        ~DisallowThrottlingScope();
+
+    private:
+        int m_savedCount;
+    };
+
     DocumentLifecycle();
     ~DocumentLifecycle();