Refactor: cleanup declarative_api.cc.

extensions/renderer/event_bindings.cc

Index: extensions/renderer/event_bindings.cc
diff --git a/extensions/renderer/event_bindings.cc b/extensions/renderer/event_bindings.cc
index bad6a02542c6d7c49943f0c6e0718015ae5f0a2f..2852c044743d70d2836c5e6b2da06547822e71f2 100644
--- a/extensions/renderer/event_bindings.cc
+++ b/extensions/renderer/event_bindings.cc
@@ -165,12 +165,15 @@ EventBindings::~EventBindings() {}
 // Attach an event name to an object.
 void EventBindings::AttachEvent(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
-  CHECK_EQ(1, args.Length());
+  CHECK_EQ(2, args.Length());
   CHECK(args[0]->IsString());
+  CHECK(args[1]->IsInt32());
 
   std::string event_name = *v8::String::Utf8Value(args[0]);
+  int guest_view_instance_id = args[1]->Int32Value();
 
-  if (!dispatcher_->CheckContextAccessToExtensionAPI(event_name, context()))
+  if (!guest_view_instance_id &&

[not at google - send to devlin, 2014/12/11 22:10:48]

If it's an int, prefer to use guest_view_instance_id == 0 rather than a boolean
expression.

[Xi Han, 2014/12/12 22:28:30]

Done.

+      !dispatcher_->CheckContextAccessToExtensionAPI(event_name, context()))

[not at google - send to devlin, 2014/12/11 22:10:48]

It's nice to surround this in {} when the condition is complex (i.e.
multi-line).

[Xi Han, 2014/12/12 22:28:30]

Done.

     return;
 

[not at google - send to devlin, 2014/12/11 22:10:48]

All the above said, it's pretty weird to see security checks being skipped here
just because it's from a webview. Could you modify the event functions to be
callable from web contexts, then you don't need this change?

[Xi Han, 2014/12/12 22:28:30]

As discussed offline, the problem here is: if passing in the event with its
original name like "declarativeWebRequest.onMessage", this event will be treated
as a regular API event, go through the permission check, and won't pass the
feature permission check here. So we do need to give <webview> event some power
to skip the check. 

   const std::string& extension_id = context()->GetExtensionID();