Defer media playback in background tabs.

chrome/renderer/chrome_content_renderer_client.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/chrome_content_renderer_client.h"
 
 #include "base/command_line.h"
 #include "base/debug/crash_logging.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
@@ skipping 323 matching lines @@
   return std::string();
 }
 #endif
 
 #if defined(ENABLE_EXTENSIONS)
 bool IsStandaloneExtensionProcess() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       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() {
   g_current_client = this;
 
 #if defined(ENABLE_EXTENSIONS)
   extensions::ExtensionsClient::Set(
       extensions::ChromeExtensionsClient::GetInstance());
   extensions::ExtensionsRendererClient::Set(
       ChromeExtensionsRendererClient::GetInstance());
@@ skipping 328 matching lines @@
 }
 
 void ChromeContentRendererClient::DeferMediaLoad(
     content::RenderFrame* render_frame,
     const base::Closure& closure) {
 #if defined(OS_ANDROID)
   // Chromium for Android doesn't support prerender yet.
   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
 }
 
 #if defined(ENABLE_PLUGINS)
 WebPlugin* ChromeContentRendererClient::CreatePlugin(
     content::RenderFrame* render_frame,
     blink::WebLocalFrame* frame,
     const WebPluginParams& original_params,
     const ChromeViewHostMsg_GetPluginInfo_Output& output) {
   const WebPluginInfo& info = output.plugin;
@@ skipping 915 matching lines @@
   WebString header_key(ASCIIToUTF16(
       data_reduction_proxy::chrome_proxy_header()));
   if (!response.httpHeaderField(header_key).isNull() &&
       response.httpHeaderField(header_key).utf8().find(
           data_reduction_proxy::chrome_proxy_lo_fi_directive()) !=
               std::string::npos) {
     (*properties)[data_reduction_proxy::chrome_proxy_header()] =
         data_reduction_proxy::chrome_proxy_lo_fi_directive();
   }
 }