Throttle rendering pipeline for invisible iframes

Source/core/frame/FrameView.h

Index: Source/core/frame/FrameView.h
diff --git a/Source/core/frame/FrameView.h b/Source/core/frame/FrameView.h
index a1b2b4383ff62b44434aa193bdc964110947d04a..4c3b3b6f528a3d5137f015067e65cdb715357837 100644
--- a/Source/core/frame/FrameView.h
+++ b/Source/core/frame/FrameView.h
@@ -226,11 +226,14 @@ public:
     Color documentBackgroundColor() const;
 
     // Run all needed lifecycle stages. After calling this method, all frames will be in the lifecycle state PaintInvalidationClean.
-    void updateAllLifecyclePhases();
+    // If lifecycle throttling is allowed, some frames may skip the lifecycle update (e.g., based on visibility) and will not end
+    // up being PaintInvalidationClean.
+    enum class LifecycleThrottlingMode { Disallow, Allow };
+    void updateAllLifecyclePhases(LifecycleThrottlingMode = LifecycleThrottlingMode::Disallow);
 
     // Computes the style, layout and compositing lifecycle stages if needed. After calling this method, all frames wil lbe in a lifecycle
     // state >= CompositingClean, and scrolling has been updated.
-    void updateLifecycleToCompositingCleanPlusScrolling();
+    void updateLifecycleToCompositingCleanPlusScrolling(LifecycleThrottlingMode = LifecycleThrottlingMode::Disallow);
 
     bool invalidateViewportConstrainedObjects();
 
@@ -559,6 +562,19 @@ public:
     void setFrameTimingRequestsDirty(bool isDirty) { m_frameTimingRequestsDirty = isDirty; }
     bool frameTimingRequestsDirty() { return m_frameTimingRequestsDirty; }
 
+    // Returns true if this frame should skip rendering pipeline processing during the
+    // current BeginMainFrame.
+    bool shouldThrottleRenderingPipeline() const;
+
+    // Returns true if this frame should skip style computation, layout and
+    // compositing updates for the current BeginMainFrame.
+    bool shouldThrottleStyleLayoutAndCompositingUpdates() const;
+
+    // Updates the throttling status of all frames in the hierarchy and
+    // schedules new animations or lifecycle updates as necessary. Must be
+    // called after the layer update phase of the current BeginMainFrame.
+    void updateThrottling();
+
 protected:
     // Scroll the content via the compositor.
     bool scrollContentsFastPath(const IntSize& scrollDelta);
@@ -612,7 +628,7 @@ private:
         OnlyUpToCompositingCleanPlusScrolling,
     };
 
-    void updateLifecyclePhasesInternal(LifeCycleUpdateOption);
+    void updateLifecyclePhasesInternal(LifeCycleUpdateOption, LifecycleThrottlingMode);
     void invalidateTreeIfNeededRecursive();
     void scrollContentsIfNeededRecursive();
     void updateStyleAndLayoutIfNeededRecursive();
@@ -717,6 +733,10 @@ private:
     void collectFrameTimingRequests(GraphicsLayerFrameTimingRequests&);
     void collectFrameTimingRequestsRecursive(GraphicsLayerFrameTimingRequests&);
 
+    void computeViewportVisibility();
+    void setLifecycleThrottlingModeRecursive(LifecycleThrottlingMode);
+    void updateThrottlingRecursive(bool hasCrossedSecurityOrigin);
+
     LayoutSize m_size;
 
     typedef HashSet<RefPtr<LayoutEmbeddedObject>> EmbeddedObjectSet;
@@ -839,6 +859,21 @@ private:
     // TODO(bokan): crbug.com/484188. We should specialize FrameView for the
     // main frame.
     OwnPtrWillBeMember<ScrollableArea> m_viewportScrollableArea;
+
+    LifecycleThrottlingMode m_lifecycleThrottlingMode;
+    // This frame's bounds in the root frame's content coordinates, clipped
+    // recursively through every ancestor view.
+    IntRect m_clippedBounds;
+
+    enum class ViewportVisibility { Hidden, Visible, Unknown };
+    ViewportVisibility m_viewportVisibility;
+
+    // The following members control rendering pipeline throttling for this
+    // frame. They are only updated at the end of the pipeline (after painting)
+    // to avoid running further pipeline stages for a frame without having gone
+    // through the previous ones.
+    ViewportVisibility m_viewportVisibilityForThrottling;
+    bool m_isCrossOriginForThrottling;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)