[Extensions] Pull ExtensionId into its own file

chrome/browser/extensions/api/declarative_content/chrome_content_rules_registry.cc

 // 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.
 
 #include "chrome/browser/extensions/api/declarative_content/chrome_content_rules_registry.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/declarative_content/content_constants.h"
 #include "chrome/browser/extensions/extension_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/api/declarative/rules_registry_service.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
+#include "extensions/common/extension_id.h"
 
 namespace extensions {
 
 //
 // EvaluationScope
 //
 
 // Used to coalesce multiple requests for evaluation into a zero or one actual
 // evaluations (depending on the EvaluationDisposition).  This is required for
 // correctness when multiple trackers respond to the same event. Otherwise,
@@ skipping 389 matching lines @@
   size_t count = 0;
   for (const auto& web_contents_rules_pair : active_rules_)
     count += web_contents_rules_pair.second.size();
   return count;
 }
 
 ChromeContentRulesRegistry::~ChromeContentRulesRegistry() {
 }
 
 }  // namespace extensions