Turn on render throttling for iframes with pending sheets.

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index 04732581f6091acba7571772a9e2c2e8ff0764d2..6ab24347da95688533190d0d57cc1b2ae5d1bd79 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -681,6 +681,8 @@ class CORE_EXPORT FrameView final
   // frame.
   void updateRenderThrottlingStatusForTesting();
 
+  void beginLifecycleUpdates();
+
   // Paint properties for SPv2 Only.
   void setPreTranslation(
       PassRefPtr<TransformPaintPropertyNode> preTranslation) {
@@ -837,6 +839,8 @@ class CORE_EXPORT FrameView final
   void scheduleOrPerformPostLayoutTasks();
   void performPostLayoutTasks();
 
+  void maybeRecordLoadReason();
+
   DocumentLifecycle& lifecycle() const;
 
   void contentsResized() override;
@@ -1046,6 +1050,7 @@ class CORE_EXPORT FrameView final
   // notifications, i.e., not in the middle of the lifecycle.
   bool m_hiddenForThrottling;
   bool m_subtreeThrottled;
+  bool m_lifecycleUpdatesThrottled;
 
   // Paint properties for SPv2 Only.
   // The hierarchy of transform subtree created by a FrameView.