Move ExtensionHost from src/chrome to src/extensions

apps/DEPS

 include_rules = [
   "+base",
   "+content/public/browser",
   "+content/public/common",
   "+content/public/test",
   "+components/keyed_service",
   "+components/user_prefs/pref_registry_syncable.h",
   "+components/web_modal",
   "+extensions",
   "+net/base",
@@ skipping 12 matching lines @@
   "+chrome/browser/sessions/session_id.h",
   "+chrome/common/chrome_switches.h",
 
   # Pieces of the extensions system that need to move to src/extensions.
   # See http://crbug.com/162530 for details.
   "+chrome/browser/extensions/api/app_runtime/app_runtime_api.h",
   "+chrome/browser/extensions/api/file_handlers/app_file_handler_util.h",
   "+chrome/browser/extensions/api/file_system/file_system_api.h",
   "+chrome/browser/extensions/chrome_extension_web_contents_observer.h",
   "+chrome/browser/extensions/extension_icon_image.h",
-  "+chrome/browser/extensions/extension_host.h",
   "+chrome/browser/extensions/suggest_permission_util.h",
   "+chrome/browser/extensions/unpacked_installer.h",
   "+chrome/common/extensions/api/app_runtime.h",
   "+chrome/common/extensions/api/app_window.h",
   "+chrome/common/extensions/manifest_handlers/icons_handler.h",
 ]
 
 specific_include_rules = {
   # Needs to be able to reload extensions. http://crbug.com/162530
   "app_load_service\.cc": [
     "+chrome/browser/extensions/extension_service.h",
   ],
   "(.*test\.cc|.*test_mac\.mm)": [
     "+chrome/browser/browser_shutdown.h",
     "+chrome/browser/extensions/extension_browsertest.h",
     "+chrome/browser/extensions/extension_test_message_listener.h",
     "+chrome/browser/extensions/test_extension_environment.h",
     "+chrome/browser/extensions/test_extension_prefs.h",
     "+chrome/browser/ui/browser.h",
     "+chrome/test/base/in_process_browser_test.h",
     "+chrome/test/base/interactive_test_utils.h",
     "+chrome/test/base/testing_profile.h",
     # Temporary allowed testing include.
     # TODO(benwells): Move app_browsertest_util into apps component once there
     # is an apps shell to test with.
     "+chrome/browser/apps/app_browsertest_util.h",
   ]
 }