Register bindings for blessed web contexts (aka hosted app contexts) by hand

chrome/renderer/extensions/runtime_custom_bindings.cc

Index: chrome/renderer/extensions/runtime_custom_bindings.cc
diff --git a/chrome/renderer/extensions/runtime_custom_bindings.cc b/chrome/renderer/extensions/runtime_custom_bindings.cc
index fd92526eb77f99d76d92c3425090a2366a41d10d..ac244b15a947e06744ebf986de45169c1a54a43d 100644
--- a/chrome/renderer/extensions/runtime_custom_bindings.cc
+++ b/chrome/renderer/extensions/runtime_custom_bindings.cc
@@ -58,7 +58,13 @@ void RuntimeCustomBindings::OpenChannelToExtension(
   CHECK(args[0]->IsString() && args[1]->IsString() && args[2]->IsBoolean());
 
   ExtensionMsg_ExternalConnectionInfo info;
-  info.source_id = context()->GetExtensionID();
+
+  // For messaging APIs, hosted apps should be considered a web page so hide
+  // its extension ID.
+  const Extension* extension = context()->extension();
+  if (extension && !extension->is_hosted_app())
+    info.source_id = extension->id();
+
   info.target_id = *v8::String::Utf8Value(args[0]->ToString());
   info.source_url = context()->GetURL();
   std::string channel_name = *v8::String::Utf8Value(args[1]->ToString());