[Extensions] Apply WARN_UNUSED_RESULT and final keyword to ExtensionFunctions.

extensions/browser/extension_function.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_
 #define EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_
 
 #include <list>
 #include <string>
 
@@ skipping 304 matching lines @@
   // Some legacy APIs do rely on it though, like webstorePrivate.
   ResponseValue ErrorWithArguments(scoped_ptr<base::ListValue> args,
                                    const std::string& error);
   // Bad message. A ResponseValue equivalent to EXTENSION_FUNCTION_VALIDATE(),
   // so this will actually kill the renderer and not respond at all.
   ResponseValue BadMessage();
 
   // ResponseActions.
   //
   // Respond to the extension immediately with |result|.
-  ResponseAction RespondNow(ResponseValue result);
+  ResponseAction RespondNow(ResponseValue result) WARN_UNUSED_RESULT;
   // Don't respond now, but promise to call Respond(...) later.
-  ResponseAction RespondLater();
+  ResponseAction RespondLater() WARN_UNUSED_RESULT;
 
   // This is the return value of the EXTENSION_FUNCTION_VALIDATE macro, which
   // needs to work from Run(), RunAsync(), and RunSync(). The former of those
   // has a different return type (ResponseAction) than the latter two (bool).
-  static ResponseAction ValidationFailure(ExtensionFunction* function);
+  static ResponseAction ValidationFailure(ExtensionFunction* function)
+      WARN_UNUSED_RESULT;
 
   // If RespondLater() was used, functions must at some point call Respond()
   // with |result| as their result.
   void Respond(ResponseValue result);
 
   virtual ~ExtensionFunction();
 
   // Helper method for ExtensionFunctionDeleteTraits. Deletes this object.
   virtual void Destruct() const = 0;
 
@@ skipping 238 matching lines @@
   //
   // AsyncExtensionFunctions implement this method. Return true to indicate that
   // nothing has gone wrong yet; SendResponse must be called later. Return false
   // to respond immediately with an error.
   virtual bool RunAsync() = 0;
 
   // ValidationFailure override to match RunAsync().
   static bool ValidationFailure(AsyncExtensionFunction* function);
 
  private:
-  ResponseAction Run() override;
+  ResponseAction Run() final;
 };
 
 // A SyncExtensionFunction is an ExtensionFunction that runs synchronously
 // *relative to the browser's UI thread*. Note that this has nothing to do with
 // running synchronously relative to the extension process. From the extension
 // process's point of view, the function is still asynchronous.
 //
 // This kind of function is convenient for implementing simple APIs that just
 // need to interact with things on the browser UI thread.
 class SyncExtensionFunction : public UIThreadExtensionFunction {
  public:
   SyncExtensionFunction();
 
  protected:
   ~SyncExtensionFunction() override;
 
   // Deprecated: Override UIThreadExtensionFunction and implement Run() instead.
   //
   // SyncExtensionFunctions implement this method. Return true to respond
   // immediately with success, false to respond immediately with an error.
   virtual bool RunSync() = 0;
 
   // ValidationFailure override to match RunSync().
   static bool ValidationFailure(SyncExtensionFunction* function);
 
  private:
-  ResponseAction Run() override;
+  ResponseAction Run() final;
 };
 
 class SyncIOThreadExtensionFunction : public IOThreadExtensionFunction {
  public:
   SyncIOThreadExtensionFunction();
 
  protected:
   ~SyncIOThreadExtensionFunction() override;
 
   // Deprecated: Override IOThreadExtensionFunction and implement Run() instead.
   //
   // SyncIOThreadExtensionFunctions implement this method. Return true to
   // respond immediately with success, false to respond immediately with an
   // error.
   virtual bool RunSync() = 0;
 
   // ValidationFailure override to match RunSync().
   static bool ValidationFailure(SyncIOThreadExtensionFunction* function);
 
  private:
-  ResponseAction Run() override;
+  ResponseAction Run() final;
 };
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_