Do not dereference potentially invalid frame pointer.

chrome/renderer/extensions/bindings_utils.h

Index: chrome/renderer/extensions/bindings_utils.h
diff --git a/chrome/renderer/extensions/bindings_utils.h b/chrome/renderer/extensions/bindings_utils.h
index 1246a1afc2b0aca4dc454217d2d949480dae1c13..958727ebcce95adf515310febb02fc958c5d9a62 100644
--- a/chrome/renderer/extensions/bindings_utils.h
+++ b/chrome/renderer/extensions/bindings_utils.h
@@ -82,20 +82,23 @@ const char* GetStringResource(int resource_id);
 // bindings.
 struct ContextInfo {
   ContextInfo(v8::Persistent<v8::Context> context,
-              const std::string& extension_id,
-              WebKit::WebFrame* frame);
+              v8::Persistent<v8::Context> main_world_context,
+              const std::string& extension_id);
   ~ContextInfo();
 
+  // The context hosting the bindings. If this is a content script, the handle
+  // will be weak.
   v8::Persistent<v8::Context> context;
 
+  // If the context is a content script, this contains a reference to the
+  // corresponding main world's context. It is weak, but it should always be
+  // valid because we delete ContextInfo for content scripts when the
+  // corresponding main world context is destroyed.
+  v8::Persistent<v8::Context> main_world_context;
+
   // The extension ID this context is associated with.
   std::string extension_id;
 
-  // The frame the context is associated with. We can't always get this from
-  // WebFrame::frameForContext() (in particular as the the frame is navigating
-  // or being destroyed).
-  WebKit::WebFrame* frame;
-
   // A count of the number of events that are listening in this context. When
   // this is zero, |context| will be a weak handle.
   int num_connected_events;