Mac: Use Mavericks occlusion APIs for power savings.

content/browser/renderer_host/render_widget_host_view_mac.h

Index: content/browser/renderer_host/render_widget_host_view_mac.h
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 33663b1ea106feda3094bed877d8a43079fa9dad..d3e68a068ad0fd478e272fbaf9b2158411b1a8ff 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -377,11 +377,42 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   // The background CoreAnimation layer which is hosted by |cocoa_view_|.
   base::scoped_nsobject<CALayer> background_layer_;
 
+  // The state of |delegated_frame_host_| and |browser_compositor_view_| to
+  // manage being visible, hidden, or occluded.
+  enum BrowserCompositorViewState {
+    // Effects:
+    // - |browser_compositor_view_| exists and |delegated_frame_host_| is
+    //    visible.
+    // Happens when:
+    // - |render_widet_host_| is in the visible state (this includes when
+    //   the tab isn't visible, but tab capture is enabled).
+    BrowserCompositorActive,
+    // Effects:
+    // - |browser_compositor_view_| exists, but |delegated_frame_host_| has
+    //   been hidden.
+    // Happens when:
+    // - The |render_widget_host_| is hidden, but |cocoa_view_| is still in the
+    //   NSWindow hierarchy.
+    // - This happens when |cocoa_view_| is occluded by another window. The

[Andre, 2014/10/30 03:19:26]

Occlusion also happens when the window is minimized, and when the app is hidden.

[ccameron, 2014/10/30 19:23:33]

Done.

+    //   |browser_compositor_view_| and its CALayers are kept around so that we
+    //   will have content to show when we are un-occluded.
+    BrowserCompositorSuspended,
+    // Effects:
+    // - |browser_compositor_view_| has been destroyed and
+    //   |delegated_frame_host_| has been hidden. This is for situations where

[miu, 2014/10/30 18:33:44]

s/This is for situations where//

[ccameron, 2014/10/30 19:23:33]

Done.

+    // Happens when:
+    // - The |render_widget_host_| is hidden or dead, and |cocoa_view_| is not
+    //   attached to a NSWindow.
+    // - This happens for backgrounded tabs.
+    BrowserCompositorDestroyed,
+  };

[Avi (use Gerrit), 2014/10/30 19:32:52]

I love these comments.

+  BrowserCompositorViewState browser_compositor_state_;
+
   // Delegated frame management and compositior.
   scoped_ptr<DelegatedFrameHost> delegated_frame_host_;
   scoped_ptr<ui::Layer> root_layer_;
 
-  // Container for the NSView drawn by the browser compositor.
+  // Container for the CALayer tree drawn by the browser compositor.
   scoped_ptr<BrowserCompositorViewMac> browser_compositor_view_;
 
   // Placeholder that is allocated while browser_compositor_view_ is NULL,
@@ -429,6 +460,10 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   void BrowserCompositorViewFrameSwapped(
       const std::vector<ui::LatencyInfo>& latency_info) override;
 
+  // Transition from being in the Suspended state to being in the Destroyed
+  // state, if appropriate (see BrowserCompositorViewState for details).
+  void DestroySuspendedBrowserCompositorViewIfNeeded();
+
  private:
   friend class RenderWidgetHostViewMacTest;
 
@@ -443,7 +478,10 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   // ensure no dangling references.
   void ShutdownBrowserCompositor();
 
+  // The state of the the browser compositor and delegated frame host. See
+  // BrowserCompositorViewState for details.
   void EnsureBrowserCompositorView();
+  void SuspendBrowserCompositorView();
   void DestroyBrowserCompositorView();
 
   // IPC message handlers.