Defer media playback in background tabs.

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index d925fe3a1f2bccdcc6b416b4c3d5e6c4ebb1f33f..06187044a9640f34ac0ec3bd1b8fa41bbdb1d2dd 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -341,6 +341,30 @@ bool IsStandaloneExtensionProcess() {
       extensions::switches::kExtensionProcess);
 }
 #endif
+
+// Defers media player loading in background pages until they're visible.
+class MediaLoadDeferrer : public content::RenderFrameObserver {
+ public:
+  MediaLoadDeferrer(content::RenderFrame* render_frame,
+                    const base::Closure& continue_loading_cb)
+      : content::RenderFrameObserver(render_frame),
+        continue_loading_cb_(continue_loading_cb) {}
+  ~MediaLoadDeferrer() override {}
+
+ private:
+  // content::RenderFrameObserver implementation:
+  void WasShown() override {
+    continue_loading_cb_.Run();
+    delete this;
+  }
+
+  // TODO(dalecurtis): Include an idle listener too.  http://crbug.com/509135
+
+  const base::Closure continue_loading_cb_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaLoadDeferrer);
+};
+
 }  // namespace
 
 ChromeContentRendererClient::ChromeContentRendererClient() {
@@ -689,13 +713,20 @@ void ChromeContentRendererClient::DeferMediaLoad(
   closure.Run();
   return;
 #else
-  if (!prerender::PrerenderHelper::IsPrerendering(render_frame)) {
+  if (prerender::PrerenderHelper::IsPrerendering(render_frame)) {
+    // Lifetime is tied to |render_frame| via content::RenderFrameObserver.
+    new prerender::PrerenderMediaLoadDeferrer(render_frame, closure);
+    return;
+  }
+
+  // TODO(dalecurtis): Include an idle check too.  http://crbug.com/509135
+  if (!render_frame->IsHidden()) {

[Lei Zhang, 2015/08/13 19:11:47]

nit, how about we structure this block consistently:

if (cond1) {
  new Foo;
  return;
}

if (cond2) {
  new Bar;
  return;
}

closure.Run();

[DaleCurtis, 2015/08/13 21:44:48]

Done.

     closure.Run();
     return;
   }
 
   // Lifetime is tied to |render_frame| via content::RenderFrameObserver.
-  new prerender::PrerenderMediaLoadDeferrer(render_frame, closure);
+  new MediaLoadDeferrer(render_frame, closure);
 #endif
 }