[Extensions] Pull ExtensionId into its own file

extensions/browser/process_manager.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_PROCESS_MANAGER_H_
 #define EXTENSIONS_BROWSER_PROCESS_MANAGER_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/event_page_tracker.h"
 #include "extensions/browser/extension_registry_observer.h"
-#include "extensions/common/extension.h"
+#include "extensions/common/extension_id.h"
 #include "extensions/common/view_type.h"
 
 class GURL;
 
 namespace content {
 class BrowserContext;
 class DevToolsAgentHost;
 class RenderFrameHost;
 class SiteInstance;
 class WebContents;
@@ skipping 294 matching lines @@
 
   // Must be last member, see doc on WeakPtrFactory.
   base::WeakPtrFactory<ProcessManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessManager);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_PROCESS_MANAGER_H_