[Extensions] Add renderer-side logic to short circuit activity logging

chrome/browser/extensions/activity_log/activity_log.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 CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_H_
 #define CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 100 matching lines @@
   // Clean up URLs from the activity log database.
   // If restrict_urls is empty then all URLs in the activity log database are
   // removed, otherwise only those in restrict_urls are removed.
   void RemoveURLs(const std::vector<GURL>& restrict_urls);
   void RemoveURLs(const std::set<GURL>& restrict_urls);
   void RemoveURL(const GURL& url);
 
   // Deletes the database associated with the policy that's currently in use.
   void DeleteDatabase();
 
+  bool is_active() const { return is_active_; }
+
   // If we're in a browser test, we need to pretend that the watchdog app is
   // active.
   void SetWatchdogAppActiveForTesting(bool active);
 
  private:
   friend class ActivityLogTest;
   friend class BrowserContextKeyedAPIFactory<ActivityLog>;
 
   explicit ActivityLog(content::BrowserContext* context);
   ~ActivityLog() override;
@@ skipping 65 matching lines @@
   // added or removed, enabled_ may change.
   ScopedObserver<extensions::ExtensionRegistry,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
 
   // Set if the watchdog app is installed and enabled. Maintained by
   // kWatchdogExtensionActive pref variable. Since there are multiple valid
   // extension IDs, this needs to be an int to count how many are installed.
   int watchdog_apps_active_;
 
-  // True if the activity log is currently active.
+  // True if the activity log is currently active, meaning that the user has
+  // either added the commandline switch or has loaded a compatible extension.
+  // While inactive, the activity log will not store any actions for performance
+  // reasons.
   bool is_active_;
 
   content::NotificationRegistrar registrar_;
 
   FRIEND_TEST_ALL_PREFIXES(ActivityLogApiTest, TriggerEvent);
   FRIEND_TEST_ALL_PREFIXES(ActivityLogEnabledTest, AppAndCommandLine);
   FRIEND_TEST_ALL_PREFIXES(ActivityLogEnabledTest, CommandLineSwitch);
   FRIEND_TEST_ALL_PREFIXES(ActivityLogEnabledTest, NoSwitch);
   FRIEND_TEST_ALL_PREFIXES(ActivityLogEnabledTest, PrefSwitch);
   FRIEND_TEST_ALL_PREFIXES(ActivityLogEnabledTest, WatchdogSwitch);
   DISALLOW_COPY_AND_ASSIGN(ActivityLog);
 };
 
 template <>
 void BrowserContextKeyedAPIFactory<ActivityLog>::DeclareFactoryDependencies();
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_H_