Plugin Power Saver: Implement pixel tests for plugin placeholders.

components/plugins/renderer/loadable_plugin_placeholder.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 COMPONENTS_PLUGINS_RENDERER_LOADABLE_PLUGIN_PLACEHOLDER_H_
 #define COMPONENTS_PLUGINS_RENDERER_LOADABLE_PLUGIN_PLACEHOLDER_H_
 
 #include "base/memory/weak_ptr.h"
 #include "base/timer/timer.h"
 #include "components/plugins/renderer/plugin_placeholder.h"
@@ skipping 54 matching lines @@
   // Replace this placeholder with a different plugin (which could be
   // a placeholder again).
   void ReplacePlugin(blink::WebPlugin* new_plugin);
 
   // Load the blocked plugin.
   void LoadPlugin();
 
   // Javascript callbacks:
   void LoadCallback();
   void DidFinishLoadingCallback();
+  void DidFinishIconRepositionForTestingCallback();
 
  private:
   // WebViewPlugin::Delegate methods:
   void PluginDestroyed() override;
   v8::Local<v8::Object> GetV8ScriptableObject(
       v8::Isolate* isolate) const override;
   void OnUnobscuredRectUpdate(const gfx::Rect& unobscured_rect) override;
 
   // RenderFrameObserver methods:
   void WasShown() override;
@@ skipping 42 matching lines @@
   bool heuristic_run_before_;
 
   base::WeakPtrFactory<LoadablePluginPlaceholder> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LoadablePluginPlaceholder);
 };
 
 }  // namespace plugins
 
 #endif  // COMPONENTS_PLUGINS_RENDERER_LOADABLE_PLUGIN_PLACEHOLDER_H_