Fix the bug that closing a tab which owns a fullscreen Flash widget causes crash.

content/renderer/render_widget_fullscreen_pepper.h

Index: content/renderer/render_widget_fullscreen_pepper.h
diff --git a/content/renderer/render_widget_fullscreen_pepper.h b/content/renderer/render_widget_fullscreen_pepper.h
index b8f095f230a47d64f91c9831ffe006a5274605e4..3742d974669c103cca9c9d8cfdf66929136285ad 100644
--- a/content/renderer/render_widget_fullscreen_pepper.h
+++ b/content/renderer/render_widget_fullscreen_pepper.h
@@ -41,6 +41,9 @@ class RenderWidgetFullscreenPepper : public RenderWidgetFullscreen,
   RendererGLContext* context() const { return context_; }
   void SwapBuffers();
 
+  // Could be NULL when this widget is closing.
+  webkit::ppapi::PluginInstance* plugin() const { return plugin_; }
+
  protected:
   RenderWidgetFullscreenPepper(webkit::ppapi::PluginInstance* plugin,
                                const GURL& active_url);