Move BrowserPluginDelegate's lifetime mgmt out of content/

content/public/renderer/browser_plugin_delegate.h

Index: content/public/renderer/browser_plugin_delegate.h
diff --git a/content/public/renderer/browser_plugin_delegate.h b/content/public/renderer/browser_plugin_delegate.h
index 583c43c4bcddcd6ed0a05654647805fdf5f19f0a..eaec84dcf9f34c7f98626c8df06d3bc349d0c6ff 100644
--- a/content/public/renderer/browser_plugin_delegate.h
+++ b/content/public/renderer/browser_plugin_delegate.h
@@ -5,8 +5,6 @@
 #ifndef CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_DELEGATE_H_
 #define CONTENT_PUBLIC_RENDERER_BROWSER_PLUGIN_DELEGATE_H_
 
-#include <string>
-
 #include "content/common/content_export.h"
 
 namespace gfx {
@@ -28,8 +26,6 @@ class RenderFrame;
 // behavior of the plugin.
 class CONTENT_EXPORT BrowserPluginDelegate {
  public:
-  virtual ~BrowserPluginDelegate() {}
-
   // Called when the BrowserPlugin's geometry has been computed for the first
   // time.
   virtual void Ready() {}
@@ -47,8 +43,14 @@ class CONTENT_EXPORT BrowserPluginDelegate {
   // Called when the plugin resizes.
   virtual void DidResizeElement(const gfx::Size& new_size) {}
 
+  // Called when the plugin is about to be destroyed.
+  virtual void DidDestroyElement() {}
+
   // Return a scriptable object for the plugin.
   virtual v8::Local<v8::Object> V8ScriptableObject(v8::Isolate* isolate);
+
+ protected:
+  virtual ~BrowserPluginDelegate() {}
 };
 
 }  // namespace content