Signal extension API schema corruption to the browser process.

extensions/common/extension_api.h

Index: extensions/common/extension_api.h
diff --git a/extensions/common/extension_api.h b/extensions/common/extension_api.h
index e876079b37858897adf6611bcfe679e5744fed8a..03a8508dcc22412d0a65616562279450de63a8b2 100644
--- a/extensions/common/extension_api.h
+++ b/extensions/common/extension_api.h
@@ -106,7 +106,8 @@ class ExtensionAPI {
   // Returns true if |name| is available to WebUI contexts on |url|.
   bool IsAvailableToWebUI(const std::string& name, const GURL& url);
 
-  // Gets the schema for the extension API with namespace |full_name|.
+  // Gets the schema for the extension API with namespace |full_name|, or
+  // nullptr if the schema could not be loaded.
   // Ownership remains with this object.
   const base::DictionaryValue* GetSchema(const std::string& full_name);