Plugin Power Saver: Add UI Overlay to throttled plugin using placeholder.

chrome/renderer/plugins/plugin_preroller.h

+// Copyright 2015 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.
+
+#ifndef CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_
+#define CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_
+
+#include "base/macros.h"
+#include "content/public/common/webplugininfo.h"
+#include "content/public/renderer/plugin_instance_throttler.h"
+#include "third_party/WebKit/public/web/WebPluginParams.h"
+#include "url/gurl.h"
+
+namespace blink {
+class WebPlugin;

[Lei Zhang, 2015/01/30 21:50:07]

nit: alphabetical order

[tommycli, 2015/02/02 18:35:47]

Done.

+class WebLocalFrame;
+}
+
+class SkBitmap;
+
+// This class manages a plugin briefly for the purposes of keyframe extraction.
+// Once a keyframe has been extracted, this class will replace it with a

[Lei Zhang, 2015/01/30 21:50:07]

replace it -> replace itself?

[tommycli, 2015/02/02 18:35:47]

Done. I changed the wording a bit.

+// ChromePluginPlaceholder. The actual plugin will continue to live in a
+// throttled state. This class manages its own lifetime.
+class PluginPreroller : public content::PluginInstanceThrottler::Observer {
+ public:
+  // Does not take ownership of either |plugin| or |throttler|.

[Lei Zhang, 2015/01/30 21:50:07]

What guarantees do you have that this outlives |plugin| ? What about
|render_frame| and |frame| ?

[tommycli, 2015/02/02 18:35:47]

This isn't meant to outlive those. But |plugin|, |render_frame| and |frame|
should outlive this class.

That's ensured by the OnThrottlerDestroyed call. I hope.

[Lei Zhang, 2015/02/02 20:34:09]

I can understand the fact that this class lives at most as long as |throttler_|,
and |plugin_| owns |throttler_|, so storing those two pointers is safe. I can't
work out the lifetime relationship between |plugin_| and |render_frame_|, but
|render_frame_| and |frame_| seems to be related.

You may want to be a RenderFrameObserver and observe |render_frame_| destruction
as well.

[tommycli, 2015/02/02 21:49:57]

Done.

+  PluginPreroller(content::RenderFrame* render_frame,
+                  blink::WebLocalFrame* frame,
+                  const blink::WebPluginParams& params,
+                  const content::WebPluginInfo& info,
+                  const std::string& identifier,
+                  const base::string16& name,
+                  const base::string16& message,
+                  blink::WebPlugin* plugin,
+                  content::PluginInstanceThrottler* throttler);
+
+  virtual ~PluginPreroller();
+
+ private:
+  // content::PluginInstanceThrottler::Observer methods:
+  void OnKeyframeExtracted(const SkBitmap* bitmap) override;
+  void OnThrottleStateChange() override;
+  void OnThrottlerDestroyed() override;
+
+  content::RenderFrame* render_frame_;
+  blink::WebLocalFrame* frame_;
+  blink::WebPluginParams params_;
+  content::WebPluginInfo info_;
+  std::string identifier_;
+  base::string16 name_;
+  base::string16 message_;
+
+  blink::WebPlugin* plugin_;
+  content::PluginInstanceThrottler* throttler_;
+
+  GURL keyframe_data_url_;
+
+  DISALLOW_COPY_AND_ASSIGN(PluginPreroller);
+};
+
+#endif  // CHROME_RENDERER_PLUGINS_PLUGIN_PREROLLER_H_