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

components/plugins/renderer/loadable_plugin_placeholder.h

Index: components/plugins/renderer/loadable_plugin_placeholder.h
diff --git a/components/plugins/renderer/loadable_plugin_placeholder.h b/components/plugins/renderer/loadable_plugin_placeholder.h
index 402fdc7e4d185b976f4d1fe19239e21284e505dc..401ec7d2995e8b03cc4759c0b12ad96ed61aca2b 100644
--- a/components/plugins/renderer/loadable_plugin_placeholder.h
+++ b/components/plugins/renderer/loadable_plugin_placeholder.h
@@ -13,7 +13,9 @@
 namespace plugins {
 // Placeholders can be used if a plug-in is missing or not available
 // (blocked or disabled).
-class LoadablePluginPlaceholder : public PluginPlaceholder {
+class LoadablePluginPlaceholder
+    : public PluginPlaceholder,
+      public content::PluginInstanceThrottler::Observer {
  public:
   void set_blocked_for_background_tab(bool blocked_for_background_tab) {
     is_blocked_for_background_tab_ = blocked_for_background_tab;
@@ -34,6 +36,10 @@ class LoadablePluginPlaceholder : public PluginPlaceholder {
 
   void set_allow_loading(bool allow_loading) { allow_loading_ = allow_loading; }
 
+  // When we load the plugin, use this already-created plugin, not a new one.
+  void SetPremadePlugin(blink::WebPlugin* plugin,
+                        content::PluginInstanceThrottler* throttler);
+
  protected:
   LoadablePluginPlaceholder(content::RenderFrame* render_frame,
                             blink::WebLocalFrame* frame,
@@ -73,11 +79,14 @@ class LoadablePluginPlaceholder : public PluginPlaceholder {
 
  private:
   // WebViewPlugin::Delegate methods:
-  void ShowContextMenu(const blink::WebMouseEvent&) override;
+  void PluginDestroyed() override;
 
   // RenderFrameObserver methods:
   void WasShown() override;
 
+  // content::PluginInstanceThrottler::Observer methods:
+  void OnThrottleStateChange() override;
+
   // Javascript callbacks:
 
   // Load the blocked plugin by calling LoadPlugin().
@@ -110,6 +119,10 @@ class LoadablePluginPlaceholder : public PluginPlaceholder {
   // This is independent of deferred plugin load due to a Power Saver poster.
   content::PluginPowerSaverMode power_saver_mode_;
 
+  // When we load, uses this premade plugin instead of creating a new one.
+  blink::WebPlugin* premade_plugin_;
+  content::PluginInstanceThrottler* premade_throttler_;
+
   bool allow_loading_;
 
   // True if the placeholder was replaced with the real plugin.