Generate all extension schema namespaces as "api" and instead vary the generated bundle names.

extensions/browser/api/app_window/app_window_api.h

 // Copyright (c) 2012 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_API_APP_WINDOW_APP_WINDOW_API_H_
 #define EXTENSIONS_BROWSER_API_APP_WINDOW_APP_WINDOW_API_H_
 
 #include "extensions/browser/app_window/app_window.h"
 #include "extensions/browser/extension_function.h"
 
 namespace extensions {
 
-namespace core_api {
+namespace api {
 namespace app_window {
 struct CreateWindowOptions;
 }
 }
 
 class AppWindowCreateFunction : public AsyncExtensionFunction {
  public:
   AppWindowCreateFunction();
   DECLARE_EXTENSION_FUNCTION("app.window.create", APP_WINDOW_CREATE)
 
  protected:
   ~AppWindowCreateFunction() override {}
   bool RunAsync() override;
 
  private:
   bool GetBoundsSpec(
-      const extensions::core_api::app_window::CreateWindowOptions& options,
+      const extensions::api::app_window::CreateWindowOptions& options,
       AppWindow::CreateParams* params,
       std::string* error);
 
   AppWindow::Frame GetFrameFromString(const std::string& frame_string);
   bool GetFrameOptions(
-      const extensions::core_api::app_window::CreateWindowOptions& options,
+      const extensions::api::app_window::CreateWindowOptions& options,
       AppWindow::CreateParams* create_params);
   void UpdateFrameOptionsForChannel(AppWindow::CreateParams* create_params);
 
   bool inject_html_titlebar_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_APP_WINDOW_APP_WINDOW_API_H_