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..26e6db7ceaf6fd9e774f1ce5af9b792989e5f149 100644
--- a/Source/core/frame/FrameView.h
+++ b/Source/core/frame/FrameView.h
@@ -26,6 +26,7 @@
 #define FrameView_h
 
 #include "core/CoreExport.h"
+#include "core/dom/DocumentLifecycle.h"
 #include "core/frame/FrameViewAutoSizeInfo.h"
 #include "core/frame/LayoutSubtreeRootList.h"
 #include "core/frame/RootFrameViewport.h"
@@ -52,7 +53,6 @@
 namespace blink {
 
 class AXObjectCache;
-class DocumentLifecycle;
 class Cursor;
 class Element;
 class FloatSize;
@@ -226,11 +226,13 @@ 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.
+    void updateAllLifecyclePhases(DocumentLifecycle::ThrottlingMode = DocumentLifecycle::ThrottlingMode::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(DocumentLifecycle::ThrottlingMode = DocumentLifecycle::ThrottlingMode::Disallow);
 
     bool invalidateViewportConstrainedObjects();
 
@@ -559,6 +561,19 @@ 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 +627,7 @@ private:
         OnlyUpToCompositingCleanPlusScrolling,
     };
 
-    void updateLifecyclePhasesInternal(LifeCycleUpdateOption);
+    void updateLifecyclePhasesInternal(LifeCycleUpdateOption, DocumentLifecycle::ThrottlingMode);
     void invalidateTreeIfNeededRecursive();
     void scrollContentsIfNeededRecursive();
     void updateStyleAndLayoutIfNeededRecursive();
@@ -717,6 +732,12 @@ private:
     void collectFrameTimingRequests(GraphicsLayerFrameTimingRequests&);
     void collectFrameTimingRequestsRecursive(GraphicsLayerFrameTimingRequests&);
 
+    void updateViewportVisibilityIfNeeded();
+    void setLifecycleThrottlingModeForSubtree(DocumentLifecycle::ThrottlingMode);
+
+    enum class SecurityOriginStatus { IsSameOrigin, IsCrossOrigin };
+    void updateThrottlingRecursive(SecurityOriginStatus);
+
     LayoutSize m_size;
 
     typedef HashSet<RefPtr<LayoutEmbeddedObject>> EmbeddedObjectSet;
@@ -801,6 +822,7 @@ private:
     float m_topControlsViewportAdjustment;
 
     bool m_needsUpdateWidgetPositions;
+    bool m_needsUpdateViewportVisibility;
 
 #if ENABLE(ASSERT)
     // Verified when finalizing.
@@ -839,6 +861,19 @@ private:
     // TODO(bokan): crbug.com/484188. We should specialize FrameView for the
     // main frame.
     OwnPtrWillBeMember<ScrollableArea> m_viewportScrollableArea;
+
+    // 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 };
+
+    // 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_viewportVisibility;
+    SecurityOriginStatus m_securityOriginStatusForThrottling;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)