Allow extension APIs to be called from WebUI.

extensions/common/extension_api.cc

Index: extensions/common/extension_api.cc
diff --git a/extensions/common/extension_api.cc b/extensions/common/extension_api.cc
index 6f67887cde87993c6d7d351b9f4b49d25483dea0..3f1748839a9892633d68e85ac14ea298970f9d1d 100644
--- a/extensions/common/extension_api.cc
+++ b/extensions/common/extension_api.cc
@@ -303,6 +303,10 @@ bool ExtensionAPI::IsAvailableInUntrustedContext(const std::string& name,
              .is_available();
 }
 
+bool ExtensionAPI::IsAvailableToWebUI(const std::string& name) {
+  return IsAvailable(name, NULL, Feature::WEBUI_CONTEXT, GURL()).is_available();
+}
+
 const base::DictionaryValue* ExtensionAPI::GetSchema(
     const std::string& full_name) {
   std::string child_name;