Mac: Use Mavericks occlusion APIs for power savings.

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 964af70950fd317c6cae5be9480859c29253accf..2e0c88997552c1dd22bf65a39ab600f49d96b5cb 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -793,14 +793,15 @@ void RenderWidgetHostViewMac::WasShown() {
 }
 
 void RenderWidgetHostViewMac::WasHidden() {
-  if (render_widget_host_->is_hidden())
-    return;
-
-  DestroyBrowserCompositorView();
+  // We want to call DestroyBrowserCompositorView on inactive tabs, but not on
+  // an active tab that is being occluded.
+  if (![cocoa_view_ window])
+    DestroyBrowserCompositorView();
 
   // If we have a renderer, then inform it that we are being hidden so it can
   // reduce its resource utilization.
-  render_widget_host_->WasHidden();
+  if (!render_widget_host_->is_hidden())
+    render_widget_host_->WasHidden();
 }
 
 void RenderWidgetHostViewMac::SetSize(const gfx::Size& size) {