Third batch adding real histogram values for extension events.

BUG=503402
R=rdevlin.cronin@chromium.org, isherman@chromium.org

Review URL: https://codereview.chromium.org/1233583005

Cr-Commit-Position: refs/heads/master@{#338972}

25 files changed, 206 insertions, 183 deletions

diff --git a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
index 9e86725..640cd00 100644
--- a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
+++ b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
@@ -184,11 +184,12 @@ BookmarkManagerPrivateEventRouter::~BookmarkManagerPrivateEventRouter() {
 }
 
 void BookmarkManagerPrivateEventRouter::DispatchEvent(
+    events::HistogramValue histogram_value,
     const std::string& event_name,
     scoped_ptr<base::ListValue> event_args) {
-  extensions::EventRouter::Get(browser_context_)
-      ->BroadcastEvent(make_scoped_ptr(new extensions::Event(
-          extensions::events::UNKNOWN, event_name, event_args.Pass())));
+  EventRouter::Get(browser_context_)
+      ->BroadcastEvent(make_scoped_ptr(
+          new Event(histogram_value, event_name, event_args.Pass())));
 }
 
 void BookmarkManagerPrivateEventRouter::BookmarkModelChanged() {}
@@ -242,7 +243,8 @@ void BookmarkManagerPrivateEventRouter::BookmarkMetaInfoChanged(
   }
 
   prev_meta_info_.clear();
-  DispatchEvent(bookmark_manager_private::OnMetaInfoChanged::kEventName,
+  DispatchEvent(events::BOOKMARK_MANAGER_PRIVATE_ON_META_INFO_CHANGED,
+                bookmark_manager_private::OnMetaInfoChanged::kEventName,
                 bookmark_manager_private::OnMetaInfoChanged::Create(
                     base::Int64ToString(node->id()), changes));
 }
@@ -298,13 +300,14 @@ BookmarkManagerPrivateDragEventRouter::
 }
 
 void BookmarkManagerPrivateDragEventRouter::DispatchEvent(
+    events::HistogramValue histogram_value,
     const std::string& event_name,
     scoped_ptr<base::ListValue> args) {
   EventRouter* event_router = EventRouter::Get(profile_);
   if (!event_router)
     return;
 
-  scoped_ptr<Event> event(new Event(events::UNKNOWN, event_name, args.Pass()));
+  scoped_ptr<Event> event(new Event(histogram_value, event_name, args.Pass()));
   event_router->BroadcastEvent(event.Pass());
 }
 
@@ -312,7 +315,8 @@ void BookmarkManagerPrivateDragEventRouter::OnDragEnter(
     const BookmarkNodeData& data) {
   if (!data.is_valid())
     return;
-  DispatchEvent(bookmark_manager_private::OnDragEnter::kEventName,
+  DispatchEvent(events::BOOKMARK_MANAGER_PRIVATE_ON_DRAG_ENTER,
+                bookmark_manager_private::OnDragEnter::kEventName,
                 bookmark_manager_private::OnDragEnter::Create(
                     *CreateApiBookmarkNodeData(profile_, data)));
 }
@@ -327,7 +331,8 @@ void BookmarkManagerPrivateDragEventRouter::OnDragLeave(
     const BookmarkNodeData& data) {
   if (!data.is_valid())
     return;
-  DispatchEvent(bookmark_manager_private::OnDragLeave::kEventName,
+  DispatchEvent(events::BOOKMARK_MANAGER_PRIVATE_ON_DRAG_LEAVE,
+                bookmark_manager_private::OnDragLeave::kEventName,
                 bookmark_manager_private::OnDragLeave::Create(
                     *CreateApiBookmarkNodeData(profile_, data)));
 }
@@ -336,7 +341,8 @@ void BookmarkManagerPrivateDragEventRouter::OnDrop(
     const BookmarkNodeData& data) {
   if (!data.is_valid())
     return;
-  DispatchEvent(bookmark_manager_private::OnDrop::kEventName,
+  DispatchEvent(events::BOOKMARK_MANAGER_PRIVATE_ON_DROP,
+                bookmark_manager_private::OnDrop::kEventName,
                 bookmark_manager_private::OnDrop::Create(
                     *CreateApiBookmarkNodeData(profile_, data)));
 
diff --git a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.h b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.h
index 67ca9dc..a5d93d3 100644
--- a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.h
+++ b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.h
@@ -48,7 +48,8 @@ class BookmarkManagerPrivateEventRouter
 
  private:
   // Helper to actually dispatch an event to extension listeners.
-  void DispatchEvent(const std::string& event_name,
+  void DispatchEvent(events::HistogramValue histogram_value,
+                     const std::string& event_name,
                      scoped_ptr<base::ListValue> event_args);
 
   // Remembers the previous meta info of a node before it was changed.
@@ -111,7 +112,8 @@ class BookmarkManagerPrivateDragEventRouter
 
  private:
   // Helper to actually dispatch an event to extension listeners.
-  void DispatchEvent(const std::string& event_name,
+  void DispatchEvent(events::HistogramValue histogram_value,
+                     const std::string& event_name,
                      scoped_ptr<base::ListValue> args);
 
   Profile* profile_;
diff --git a/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc b/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
index 8db4a81..4fe297f 100644
--- a/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
+++ b/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
@@ -254,12 +254,13 @@ BookmarkEventRouter::~BookmarkEventRouter() {
 }
 
 void BookmarkEventRouter::DispatchEvent(
+    events::HistogramValue histogram_value,
     const std::string& event_name,
     scoped_ptr<base::ListValue> event_args) {
   EventRouter* event_router = EventRouter::Get(browser_context_);
   if (event_router) {
-    event_router->BroadcastEvent(make_scoped_ptr(new extensions::Event(
-        extensions::events::UNKNOWN, event_name, event_args.Pass())));
+    event_router->BroadcastEvent(make_scoped_ptr(
+        new extensions::Event(histogram_value, event_name, event_args.Pass())));
   }
 }
 
@@ -286,7 +287,7 @@ void BookmarkEventRouter::BookmarkNodeMoved(BookmarkModel* model,
   move_info.old_index = old_index;
 
   DispatchEvent(
-      bookmarks::OnMoved::kEventName,
+      events::BOOKMARKS_ON_MOVED, bookmarks::OnMoved::kEventName,
       bookmarks::OnMoved::Create(base::Int64ToString(node->id()), move_info));
 }
 
@@ -296,7 +297,7 @@ void BookmarkEventRouter::BookmarkNodeAdded(BookmarkModel* model,
   const BookmarkNode* node = parent->GetChild(index);
   scoped_ptr<BookmarkTreeNode> tree_node(
       bookmark_api_helpers::GetBookmarkTreeNode(client_, node, false, false));
-  DispatchEvent(bookmarks::OnCreated::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_CREATED, bookmarks::OnCreated::kEventName,
                 bookmarks::OnCreated::Create(base::Int64ToString(node->id()),
                                              *tree_node));
 }
@@ -311,7 +312,7 @@ void BookmarkEventRouter::BookmarkNodeRemoved(
   remove_info.parent_id = base::Int64ToString(parent->id());
   remove_info.index = index;
 
-  DispatchEvent(bookmarks::OnRemoved::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_REMOVED, bookmarks::OnRemoved::kEventName,
                 bookmarks::OnRemoved::Create(base::Int64ToString(node->id()),
                                              remove_info));
 }
@@ -337,7 +338,7 @@ void BookmarkEventRouter::BookmarkNodeChanged(BookmarkModel* model,
   if (node->is_url())
     change_info.url.reset(new std::string(node->url().spec()));
 
-  DispatchEvent(bookmarks::OnChanged::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_CHANGED, bookmarks::OnChanged::kEventName,
                 bookmarks::OnChanged::Create(base::Int64ToString(node->id()),
                                              change_info));
 }
@@ -357,19 +358,22 @@ void BookmarkEventRouter::BookmarkNodeChildrenReordered(
     reorder_info.child_ids.push_back(base::Int64ToString(child->id()));
   }
 
-  DispatchEvent(bookmarks::OnChildrenReordered::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_CHILDREN_REORDERED,
+                bookmarks::OnChildrenReordered::kEventName,
                 bookmarks::OnChildrenReordered::Create(
                     base::Int64ToString(node->id()), reorder_info));
 }
 
 void BookmarkEventRouter::ExtensiveBookmarkChangesBeginning(
     BookmarkModel* model) {
-  DispatchEvent(bookmarks::OnImportBegan::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_IMPORT_BEGAN,
+                bookmarks::OnImportBegan::kEventName,
                 bookmarks::OnImportBegan::Create());
 }
 
 void BookmarkEventRouter::ExtensiveBookmarkChangesEnded(BookmarkModel* model) {
-  DispatchEvent(bookmarks::OnImportEnded::kEventName,
+  DispatchEvent(events::BOOKMARKS_ON_IMPORT_ENDED,
+                bookmarks::OnImportEnded::kEventName,
                 bookmarks::OnImportEnded::Create());
 }
 
diff --git a/chrome/browser/extensions/api/bookmarks/bookmarks_api.h b/chrome/browser/extensions/api/bookmarks/bookmarks_api.h
index 9c3f082..2ea2857 100644
--- a/chrome/browser/extensions/api/bookmarks/bookmarks_api.h
+++ b/chrome/browser/extensions/api/bookmarks/bookmarks_api.h
@@ -76,7 +76,8 @@ class BookmarkEventRouter : public bookmarks::BookmarkModelObserver {
 
  private:
   // Helper to actually dispatch an event to extension listeners.
-  void DispatchEvent(const std::string& event_name,
+  void DispatchEvent(events::HistogramValue histogram_value,
+                     const std::string& event_name,
                      scoped_ptr<base::ListValue> event_args);
 
   content::BrowserContext* browser_context_;
diff --git a/chrome/browser/extensions/api/braille_display_private/braille_display_private_api.cc b/chrome/browser/extensions/api/braille_display_private/braille_display_private_api.cc
index cd8e56e..5a5ef77 100644
--- a/chrome/browser/extensions/api/braille_display_private/braille_display_private_api.cc
+++ b/chrome/browser/extensions/api/braille_display_private/braille_display_private_api.cc
@@ -63,7 +63,8 @@ BrailleDisplayPrivateAPI::GetFactoryInstance() {
 void BrailleDisplayPrivateAPI::OnBrailleDisplayStateChanged(
     const DisplayState& display_state) {
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, OnDisplayStateChanged::kEventName,
+      new Event(events::BRAILLE_DISPLAY_PRIVATE_ON_DISPLAY_STATE_CHANGED,
+                OnDisplayStateChanged::kEventName,
                 OnDisplayStateChanged::Create(display_state)));
   event_delegate_->BroadcastEvent(event.Pass());
 }
@@ -72,8 +73,9 @@ void BrailleDisplayPrivateAPI::OnBrailleKeyEvent(const KeyEvent& key_event) {
   // Key events only go to extensions of the active profile.
   if (!IsProfileActive())
     return;
-  scoped_ptr<Event> event(new Event(events::UNKNOWN, OnKeyEvent::kEventName,
-                                    OnKeyEvent::Create(key_event)));
+  scoped_ptr<Event> event(
+      new Event(events::BRAILLE_DISPLAY_PRIVATE_ON_KEY_EVENT,
+                OnKeyEvent::kEventName, OnKeyEvent::Create(key_event)));
   event_delegate_->BroadcastEvent(event.Pass());
 }
 
diff --git a/chrome/browser/extensions/api/cookies/cookies_api.cc b/chrome/browser/extensions/api/cookies/cookies_api.cc
index 14acc20..e91b1fc 100644
--- a/chrome/browser/extensions/api/cookies/cookies_api.cc
+++ b/chrome/browser/extensions/api/cookies/cookies_api.cc
@@ -35,18 +35,16 @@
 #include "net/url_request/url_request_context_getter.h"
 
 using content::BrowserThread;
-using extensions::api::cookies::Cookie;
-using extensions::api::cookies::CookieStore;
-
-namespace Get = extensions::api::cookies::Get;
-namespace GetAll = extensions::api::cookies::GetAll;
-namespace GetAllCookieStores = extensions::api::cookies::GetAllCookieStores;
-namespace Remove = extensions::api::cookies::Remove;
-namespace Set = extensions::api::cookies::Set;
 
 namespace extensions {
+
 namespace cookies = api::cookies;
 namespace keys = cookies_api_constants;
+namespace Get = cookies::Get;
+namespace GetAll = cookies::GetAll;
+namespace GetAllCookieStores = cookies::GetAllCookieStores;
+namespace Remove = cookies::Remove;
+namespace Set = cookies::Set;
 
 namespace {
 
@@ -143,9 +141,8 @@ void CookiesEventRouter::CookieChanged(
   base::DictionaryValue* dict = new base::DictionaryValue();
   dict->SetBoolean(keys::kRemovedKey, details->removed);
 
-  scoped_ptr<Cookie> cookie(
-      cookies_helpers::CreateCookie(*details->cookie,
-          cookies_helpers::GetStoreIdFromProfile(profile)));
+  scoped_ptr<cookies::Cookie> cookie(cookies_helpers::CreateCookie(
+      *details->cookie, cookies_helpers::GetStoreIdFromProfile(profile)));
   dict->Set(keys::kCookieKey, cookie->ToValue().release());
 
   // Map the internal cause to an external string.
@@ -180,21 +177,20 @@ void CookiesEventRouter::CookieChanged(
 
   GURL cookie_domain =
       cookies_helpers::GetURLFromCanonicalCookie(*details->cookie);
-  DispatchEvent(profile,
-                cookies::OnChanged::kEventName,
-                args.Pass(),
-                cookie_domain);
+  DispatchEvent(profile, events::COOKIES_ON_CHANGED,
+                cookies::OnChanged::kEventName, args.Pass(), cookie_domain);
 }
 
 void CookiesEventRouter::DispatchEvent(content::BrowserContext* context,
+                                       events::HistogramValue histogram_value,
                                        const std::string& event_name,
                                        scoped_ptr<base::ListValue> event_args,
                                        GURL& cookie_domain) {
-  EventRouter* router = context ? extensions::EventRouter::Get(context) : NULL;
+  EventRouter* router = context ? EventRouter::Get(context) : NULL;
   if (!router)
     return;
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, event_name, event_args.Pass()));
+      new Event(histogram_value, event_name, event_args.Pass()));
   event->restrict_to_browser_context = context;
   event->event_url = cookie_domain;
   router->BroadcastEvent(event.Pass());
@@ -251,7 +247,7 @@ void CookiesGetFunction::GetCookieCallback(const net::CookieList& cookie_list) {
     // CookieMonster returns them in canonical order (longest path, then
     // earliest creation time).
     if (it->Name() == parsed_args_->details.name) {
-      scoped_ptr<Cookie> cookie(
+      scoped_ptr<cookies::Cookie> cookie(
           cookies_helpers::CreateCookie(*it, *parsed_args_->details.store_id));
       results_ = Get::Results::Create(*cookie);
       break;
@@ -319,7 +315,7 @@ void CookiesGetAllFunction::GetAllCookiesOnIOThread() {
 void CookiesGetAllFunction::GetAllCookiesCallback(
     const net::CookieList& cookie_list) {
   if (extension()) {
-    std::vector<linked_ptr<Cookie> > match_vector;
+    std::vector<linked_ptr<cookies::Cookie>> match_vector;
     cookies_helpers::AppendMatchingCookiesToVector(
         cookie_list, url_, &parsed_args_->details, extension(), &match_vector);
 
@@ -431,7 +427,7 @@ void CookiesSetFunction::PullCookieCallback(
         parsed_args_->details.name.get() ? *parsed_args_->details.name
                                          : std::string();
     if (it->Name() == name) {
-      scoped_ptr<Cookie> cookie(
+      scoped_ptr<cookies::Cookie> cookie(
           cookies_helpers::CreateCookie(*it, *parsed_args_->details.store_id));
       results_ = Set::Results::Create(*cookie);
       break;
@@ -546,7 +542,7 @@ bool CookiesGetAllCookieStoresFunction::RunSync() {
     }
   }
   // Return a list of all cookie stores with at least one open tab.
-  std::vector<linked_ptr<CookieStore> > cookie_stores;
+  std::vector<linked_ptr<cookies::CookieStore>> cookie_stores;
   if (original_tab_ids->GetSize() > 0) {
     cookie_stores.push_back(make_linked_ptr(
         cookies_helpers::CreateCookieStore(
@@ -583,8 +579,7 @@ BrowserContextKeyedAPIFactory<CookiesAPI>* CookiesAPI::GetFactoryInstance() {
   return g_factory.Pointer();
 }
 
-void CookiesAPI::OnListenerAdded(
-    const extensions::EventListenerInfo& details) {
+void CookiesAPI::OnListenerAdded(const EventListenerInfo& details) {
   cookies_event_router_.reset(new CookiesEventRouter(browser_context_));
   EventRouter::Get(browser_context_)->UnregisterObserver(this);
 }
diff --git a/chrome/browser/extensions/api/cookies/cookies_api.h b/chrome/browser/extensions/api/cookies/cookies_api.h
index 30e2c30..0ee1180 100644
--- a/chrome/browser/extensions/api/cookies/cookies_api.h
+++ b/chrome/browser/extensions/api/cookies/cookies_api.h
@@ -48,6 +48,7 @@ class CookiesEventRouter : public content::NotificationObserver {
 
   // This method dispatches events to the extension message service.
   void DispatchEvent(content::BrowserContext* context,
+                     events::HistogramValue histogram_value,
                      const std::string& event_name,
                      scoped_ptr<base::ListValue> event_args,
                      GURL& cookie_domain);
@@ -80,7 +81,7 @@ class CookiesGetFunction : public ChromeAsyncExtensionFunction {
 
   GURL url_;
   scoped_refptr<net::URLRequestContextGetter> store_browser_context_;
-  scoped_ptr<extensions::api::cookies::Get::Params> parsed_args_;
+  scoped_ptr<api::cookies::Get::Params> parsed_args_;
 };
 
 // Implements the cookies.getAll() extension function.
@@ -103,7 +104,7 @@ class CookiesGetAllFunction : public ChromeAsyncExtensionFunction {
 
   GURL url_;
   scoped_refptr<net::URLRequestContextGetter> store_browser_context_;
-  scoped_ptr<extensions::api::cookies::GetAll::Params> parsed_args_;
+  scoped_ptr<api::cookies::GetAll::Params> parsed_args_;
 };
 
 // Implements the cookies.set() extension function.
@@ -126,7 +127,7 @@ class CookiesSetFunction : public ChromeAsyncExtensionFunction {
   GURL url_;
   bool success_;
   scoped_refptr<net::URLRequestContextGetter> store_browser_context_;
-  scoped_ptr<extensions::api::cookies::Set::Params> parsed_args_;
+  scoped_ptr<api::cookies::Set::Params> parsed_args_;
 };
 
 // Implements the cookies.remove() extension function.
@@ -149,7 +150,7 @@ class CookiesRemoveFunction : public ChromeAsyncExtensionFunction {
 
   GURL url_;
   scoped_refptr<net::URLRequestContextGetter> store_browser_context_;
-  scoped_ptr<extensions::api::cookies::Remove::Params> parsed_args_;
+  scoped_ptr<api::cookies::Remove::Params> parsed_args_;
 };
 
 // Implements the cookies.getAllCookieStores() extension function.
@@ -165,8 +166,7 @@ class CookiesGetAllCookieStoresFunction : public ChromeSyncExtensionFunction {
   bool RunSync() override;
 };
 
-class CookiesAPI : public BrowserContextKeyedAPI,
-                   public extensions::EventRouter::Observer {
+class CookiesAPI : public BrowserContextKeyedAPI, public EventRouter::Observer {
  public:
   explicit CookiesAPI(content::BrowserContext* context);
   ~CookiesAPI() override;
@@ -178,7 +178,7 @@ class CookiesAPI : public BrowserContextKeyedAPI,
   static BrowserContextKeyedAPIFactory<CookiesAPI>* GetFactoryInstance();
 
   // EventRouter::Observer implementation.
-  void OnListenerAdded(const extensions::EventListenerInfo& details) override;
+  void OnListenerAdded(const EventListenerInfo& details) override;
 
  private:
   friend class BrowserContextKeyedAPIFactory<CookiesAPI>;
diff --git a/chrome/browser/extensions/api/copresence/copresence_api.cc b/chrome/browser/extensions/api/copresence/copresence_api.cc
index c47530e..e32e0c8 100644
--- a/chrome/browser/extensions/api/copresence/copresence_api.cc
+++ b/chrome/browser/extensions/api/copresence/copresence_api.cc
@@ -147,10 +147,10 @@ void CopresenceService::HandleMessages(
   }
 
   // Send the messages to the client app.
-  scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, OnMessagesReceived::kEventName,
-                OnMessagesReceived::Create(subscription_id, api_messages),
-                browser_context_));
+  scoped_ptr<Event> event(new Event(
+      events::COPRESENCE_ON_MESSAGES_RECEIVED, OnMessagesReceived::kEventName,
+      OnMessagesReceived::Create(subscription_id, api_messages),
+      browser_context_));
   EventRouter::Get(browser_context_)
       ->DispatchEventToExtension(app_id, event.Pass());
   DVLOG(2) << "Passed " << api_messages.size() << " messages to app \""
@@ -160,10 +160,10 @@ void CopresenceService::HandleMessages(
 void CopresenceService::HandleStatusUpdate(
     copresence::CopresenceStatus status) {
   DCHECK_EQ(copresence::AUDIO_FAIL, status);
-  scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, OnStatusUpdated::kEventName,
-                OnStatusUpdated::Create(api::copresence::STATUS_AUDIOFAILED),
-                browser_context_));
+  scoped_ptr<Event> event(new Event(
+      events::COPRESENCE_ON_STATUS_UPDATED, OnStatusUpdated::kEventName,
+      OnStatusUpdated::Create(api::copresence::STATUS_AUDIOFAILED),
+      browser_context_));
   EventRouter::Get(browser_context_)->BroadcastEvent(event.Pass());
   DVLOG(2) << "Sent Audio Failed status update.";
 }
diff --git a/chrome/browser/extensions/api/debugger/debugger_api.cc b/chrome/browser/extensions/api/debugger/debugger_api.cc
index ee5d0ff3..7579503 100644
--- a/chrome/browser/extensions/api/debugger/debugger_api.cc
+++ b/chrome/browser/extensions/api/debugger/debugger_api.cc
@@ -400,7 +400,7 @@ void ExtensionDevToolsClientHost::SendDetachedEvent() {
   scoped_ptr<base::ListValue> args(OnDetach::Create(debuggee_,
                                                     detach_reason_));
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, OnDetach::kEventName, args.Pass()));
+      new Event(events::DEBUGGER_ON_DETACH, OnDetach::kEventName, args.Pass()));
   event->restrict_to_browser_context = profile_;
   EventRouter::Get(profile_)
       ->DispatchEventToExtension(extension_id_, event.Pass());
@@ -461,7 +461,7 @@ void ExtensionDevToolsClientHost::DispatchProtocolMessage(
     scoped_ptr<base::ListValue> args(
         OnEvent::Create(debuggee_, method_name, params));
     scoped_ptr<Event> event(
-        new Event(events::UNKNOWN, OnEvent::kEventName, args.Pass()));
+        new Event(events::DEBUGGER_ON_EVENT, OnEvent::kEventName, args.Pass()));
     event->restrict_to_browser_context = profile_;
     EventRouter::Get(profile_)
         ->DispatchEventToExtension(extension_id_, event.Pass());
diff --git a/chrome/browser/extensions/api/developer_private/developer_private_api.cc b/chrome/browser/extensions/api/developer_private/developer_private_api.cc
index 66d3eb5..13b8e3a 100644
--- a/chrome/browser/extensions/api/developer_private/developer_private_api.cc
+++ b/chrome/browser/extensions/api/developer_private/developer_private_api.cc
@@ -341,8 +341,8 @@ void DeveloperPrivateEventRouter::OnExtensionManagementSettingsChanged() {
   scoped_ptr<base::ListValue> args(new base::ListValue());
   args->Append(CreateProfileInfo(profile_)->ToValue());
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, developer::OnProfileStateChanged::kEventName,
-                args.Pass()));
+      new Event(events::DEVELOPER_PRIVATE_ON_PROFILE_STATE_CHANGED,
+                developer::OnProfileStateChanged::kEventName, args.Pass()));
   event_router_->BroadcastEvent(event.Pass());
 }
 
@@ -390,8 +390,9 @@ void DeveloperPrivateEventRouter::BroadcastItemStateChangedHelper(
 
   scoped_ptr<base::ListValue> args(new base::ListValue());
   args->Append(dict.release());
-  scoped_ptr<Event> event(new Event(
-      events::UNKNOWN, developer::OnItemStateChanged::kEventName, args.Pass()));
+  scoped_ptr<Event> event(
+      new Event(events::DEVELOPER_PRIVATE_ON_ITEM_STATE_CHANGED,
+                developer::OnItemStateChanged::kEventName, args.Pass()));
   event_router_->BroadcastEvent(event.Pass());
 }
 
diff --git a/chrome/browser/extensions/api/dial/dial_api.cc b/chrome/browser/extensions/api/dial/dial_api.cc
index 3e3dd17..cc9f1c6 100644
--- a/chrome/browser/extensions/api/dial/dial_api.cc
+++ b/chrome/browser/extensions/api/dial/dial_api.cc
@@ -105,8 +105,9 @@ void DialAPI::SendEventOnUIThread(const DialRegistry::DeviceList& devices) {
     args.push_back(api_device);
   }
   scoped_ptr<base::ListValue> results = api::dial::OnDeviceList::Create(args);
-  scoped_ptr<Event> event(new Event(
-      events::UNKNOWN, dial::OnDeviceList::kEventName, results.Pass()));
+  scoped_ptr<Event> event(new Event(events::DIAL_ON_DEVICE_LIST,
+                                    dial::OnDeviceList::kEventName,
+                                    results.Pass()));
   EventRouter::Get(profile_)->BroadcastEvent(event.Pass());
 }
 
@@ -136,8 +137,8 @@ void DialAPI::SendErrorOnUIThread(const DialRegistry::DialErrorCode code) {
   }
 
   scoped_ptr<base::ListValue> results = api::dial::OnError::Create(dial_error);
-  scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, dial::OnError::kEventName, results.Pass()));
+  scoped_ptr<Event> event(new Event(events::DIAL_ON_ERROR,
+                                    dial::OnError::kEventName, results.Pass()));
   EventRouter::Get(profile_)->BroadcastEvent(event.Pass());
 }
 
diff --git a/chrome/browser/extensions/api/downloads/downloads_api.cc b/chrome/browser/extensions/api/downloads/downloads_api.cc
index 4e3bc13c..b1fde95 100644
--- a/chrome/browser/extensions/api/downloads/downloads_api.cc
+++ b/chrome/browser/extensions/api/downloads/downloads_api.cc
@@ -1592,11 +1592,10 @@ void ExtensionDownloadsEventRouter::OnDeterminingFilename(
   base::DictionaryValue* json = DownloadItemToJSON(
       item, profile_).release();
   json->SetString(kFilenameKey, suggested_path.LossyDisplayName());
-  DispatchEvent(downloads::OnDeterminingFilename::kEventName,
-                false,
+  DispatchEvent(events::DOWNLOADS_ON_DETERMINING_FILENAME,
+                downloads::OnDeterminingFilename::kEventName, false,
                 base::Bind(&OnDeterminingFilenameWillDispatchCallback,
-                           &any_determiners,
-                           data),
+                           &any_determiners, data),
                 json);
   if (!any_determiners) {
     data->ClearPendingDeterminers();
@@ -1757,10 +1756,8 @@ void ExtensionDownloadsEventRouter::OnDownloadCreated(
   }
   scoped_ptr<base::DictionaryValue> json_item(
       DownloadItemToJSON(download_item, profile_));
-  DispatchEvent(downloads::OnCreated::kEventName,
-                true,
-                Event::WillDispatchCallback(),
-                json_item->DeepCopy());
+  DispatchEvent(events::DOWNLOADS_ON_CREATED, downloads::OnCreated::kEventName,
+                true, Event::WillDispatchCallback(), json_item->DeepCopy());
   if (!ExtensionDownloadsEventRouterData::Get(download_item) &&
       (router->HasEventListener(downloads::OnChanged::kEventName) ||
        router->HasEventListener(
@@ -1829,10 +1826,9 @@ void ExtensionDownloadsEventRouter::OnDownloadUpdated(
   // changed. Replace the stored json with the new json.
   data->OnItemUpdated();
   if (changed) {
-    DispatchEvent(downloads::OnChanged::kEventName,
-                  true,
-                  Event::WillDispatchCallback(),
-                  delta.release());
+    DispatchEvent(events::DOWNLOADS_ON_CHANGED,
+                  downloads::OnChanged::kEventName, true,
+                  Event::WillDispatchCallback(), delta.release());
     data->OnChangedFired();
   }
   data->set_json(new_json.Pass());
@@ -1844,13 +1840,13 @@ void ExtensionDownloadsEventRouter::OnDownloadRemoved(
   if (download_item->IsTemporary())
     return;
   DispatchEvent(
-      downloads::OnErased::kEventName,
-      true,
+      events::DOWNLOADS_ON_ERASED, downloads::OnErased::kEventName, true,
       Event::WillDispatchCallback(),
       new base::FundamentalValue(static_cast<int>(download_item->GetId())));
 }
 
 void ExtensionDownloadsEventRouter::DispatchEvent(
+    events::HistogramValue histogram_value,
     const std::string& event_name,
     bool include_incognito,
     const Event::WillDispatchCallback& will_dispatch_callback,
@@ -1862,7 +1858,7 @@ void ExtensionDownloadsEventRouter::DispatchEvent(
   args->Append(arg);
   std::string json_args;
   base::JSONWriter::Write(*args, &json_args);
-  scoped_ptr<Event> event(new Event(events::UNKNOWN, event_name, args.Pass()));
+  scoped_ptr<Event> event(new Event(histogram_value, event_name, args.Pass()));
   // The downloads system wants to share on-record events with off-record
   // extension renderers even in incognito_split_mode because that's how
   // chrome://downloads works. The "restrict_to_profile" mechanism does not
diff --git a/chrome/browser/extensions/api/downloads/downloads_api.h b/chrome/browser/extensions/api/downloads/downloads_api.h
index abd4e48..6d514a7 100644
--- a/chrome/browser/extensions/api/downloads/downloads_api.h
+++ b/chrome/browser/extensions/api/downloads/downloads_api.h
@@ -383,6 +383,7 @@ class ExtensionDownloadsEventRouter
 
  private:
   void DispatchEvent(
+      events::HistogramValue histogram_value,
       const std::string& event_name,
       bool include_incognito,
       const extensions::Event::WillDispatchCallback& will_dispatch_callback,
diff --git a/chrome/browser/extensions/api/experience_sampling_private/experience_sampling.cc b/chrome/browser/extensions/api/experience_sampling_private/experience_sampling.cc
index e7d5908..8a62c9c 100644
--- a/chrome/browser/extensions/api/experience_sampling_private/experience_sampling.cc
+++ b/chrome/browser/extensions/api/experience_sampling_private/experience_sampling.cc
@@ -84,8 +84,8 @@ void ExperienceSamplingEvent::CreateUserDecisionEvent(
   args->Append(ui_element_.ToValue().release());
   args->Append(decision.ToValue().release());
   scoped_ptr<Event> event(new Event(
-      events::UNKNOWN, api::experience_sampling_private::OnDecision::kEventName,
-      args.Pass()));
+      events::EXPERIENCE_SAMPLING_PRIVATE_ON_DECISION,
+      api::experience_sampling_private::OnDecision::kEventName, args.Pass()));
   EventRouter* router = EventRouter::Get(browser_context_);
   if (router)
     router->BroadcastEvent(event.Pass());
@@ -99,7 +99,7 @@ void ExperienceSamplingEvent::CreateOnDisplayedEvent() {
   scoped_ptr<base::ListValue> args(new base::ListValue());
   args->Append(ui_element_.ToValue().release());
   scoped_ptr<Event> event(new Event(
-      events::UNKNOWN,
+      events::EXPERIENCE_SAMPLING_PRIVATE_ON_DISPLAYED,
       api::experience_sampling_private::OnDisplayed::kEventName, args.Pass()));
   EventRouter* router = EventRouter::Get(browser_context_);
   if (router)
diff --git a/chrome/browser/extensions/api/extension_action/extension_action_api.cc b/chrome/browser/extensions/api/extension_action/extension_action_api.cc
index 917d42d..aac3d31 100644
--- a/chrome/browser/extensions/api/extension_action/extension_action_api.cc
+++ b/chrome/browser/extensions/api/extension_action/extension_action_api.cc
@@ -300,13 +300,14 @@ ExtensionPrefs* ExtensionActionAPI::GetExtensionPrefs() {
 void ExtensionActionAPI::DispatchEventToExtension(
     content::BrowserContext* context,
     const std::string& extension_id,
+    events::HistogramValue histogram_value,
     const std::string& event_name,
     scoped_ptr<base::ListValue> event_args) {
   if (!EventRouter::Get(context))
     return;
 
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, event_name, event_args.Pass()));
+      new Event(histogram_value, event_name, event_args.Pass()));
   event->restrict_to_browser_context = context;
   event->user_gesture = EventRouter::USER_GESTURE_ENABLED;
   EventRouter::Get(context)
@@ -316,16 +317,20 @@ void ExtensionActionAPI::DispatchEventToExtension(
 void ExtensionActionAPI::ExtensionActionExecuted(
     const ExtensionAction& extension_action,
     WebContents* web_contents) {
+  events::HistogramValue histogram_value = events::UNKNOWN;
   const char* event_name = NULL;
   switch (extension_action.action_type()) {
     case ActionInfo::TYPE_BROWSER:
+      histogram_value = events::BROWSER_ACTION_ON_CLICKED;
       event_name = "browserAction.onClicked";
       break;
     case ActionInfo::TYPE_PAGE:
+      histogram_value = events::PAGE_ACTION_ON_CLICKED;
       event_name = "pageAction.onClicked";
       break;
     case ActionInfo::TYPE_SYSTEM_INDICATOR:
       // The System Indicator handles its own clicks.
+      NOTREACHED();
       break;
   }
 
@@ -335,11 +340,9 @@ void ExtensionActionAPI::ExtensionActionExecuted(
         ExtensionTabUtil::CreateTabValue(web_contents);
     args->Append(tab_value);
 
-    DispatchEventToExtension(
-        web_contents->GetBrowserContext(),
-        extension_action.extension_id(),
-        event_name,
-        args.Pass());
+    DispatchEventToExtension(web_contents->GetBrowserContext(),
+                             extension_action.extension_id(), histogram_value,
+                             event_name, args.Pass());
   }
 }
 
diff --git a/chrome/browser/extensions/api/extension_action/extension_action_api.h b/chrome/browser/extensions/api/extension_action/extension_action_api.h
index 61ab75b..079b890 100644
--- a/chrome/browser/extensions/api/extension_action/extension_action_api.h
+++ b/chrome/browser/extensions/api/extension_action/extension_action_api.h
@@ -13,6 +13,7 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
+#include "extensions/browser/extension_event_histogram_value.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 namespace base {
@@ -125,6 +126,7 @@ class ExtensionActionAPI : public BrowserContextKeyedAPI {
   // The DispatchEvent methods forward events to the |context|'s event router.
   void DispatchEventToExtension(content::BrowserContext* context,
                                 const std::string& extension_id,
+                                events::HistogramValue histogram_value,
                                 const std::string& event_name,
                                 scoped_ptr<base::ListValue> event_args);
 
diff --git a/chrome/browser/extensions/api/feedback_private/feedback_private_api.cc b/chrome/browser/extensions/api/feedback_private/feedback_private_api.cc
index ad56efd..ae82f7a 100644
--- a/chrome/browser/extensions/api/feedback_private/feedback_private_api.cc
+++ b/chrome/browser/extensions/api/feedback_private/feedback_private_api.cc
@@ -89,8 +89,8 @@ void FeedbackPrivateAPI::RequestFeedback(
     args->Append(info.ToValue().release());
 
     scoped_ptr<Event> event(new Event(
-        events::UNKNOWN, feedback_private::OnFeedbackRequested::kEventName,
-        args.Pass()));
+        events::FEEDBACK_PRIVATE_ON_FEEDBACK_REQUESTED,
+        feedback_private::OnFeedbackRequested::kEventName, args.Pass()));
     event->restrict_to_browser_context = browser_context_;
 
     EventRouter::Get(browser_context_)
diff --git a/chrome/browser/extensions/api/file_system/file_system_api.cc b/chrome/browser/extensions/api/file_system/file_system_api.cc
index 68f8cab..3f033d4 100644
--- a/chrome/browser/extensions/api/file_system/file_system_api.cc
+++ b/chrome/browser/extensions/api/file_system/file_system_api.cc
@@ -117,7 +117,9 @@ const char* const kRequestFileSystemComponentWhitelist[] = {
 };
 #endif
 
-namespace file_system = extensions::api::file_system;
+namespace extensions {
+
+namespace file_system = api::file_system;
 namespace ChooseEntry = file_system::ChooseEntry;
 
 namespace {
@@ -233,7 +235,7 @@ content::WebContents* GetWebContentsForRenderFrameHost(
       content::WebContents::FromRenderFrameHost(render_frame_host);
   // Check if there is an app window associated with the web contents; if not,
   // return null.
-  return extensions::AppWindowRegistry::Get(profile)
+  return AppWindowRegistry::Get(profile)
                  ->GetAppWindowForWebContents(web_contents)
              ? web_contents
              : nullptr;
@@ -244,23 +246,20 @@ content::WebContents* GetWebContentsForRenderFrameHost(
 // with |app_id|. If not found, then returns NULL.
 content::WebContents* GetWebContentsForAppId(Profile* profile,
                                              const std::string& app_id) {
-  extensions::AppWindowRegistry* const registry =
-      extensions::AppWindowRegistry::Get(profile);
+  AppWindowRegistry* const registry = AppWindowRegistry::Get(profile);
   DCHECK(registry);
-  extensions::AppWindow* const app_window =
-      registry->GetCurrentAppWindowForApp(app_id);
+  AppWindow* const app_window = registry->GetCurrentAppWindowForApp(app_id);
   return app_window ? app_window->web_contents() : nullptr;
 }
 
 // Fills a list of volumes mounted in the system.
-void FillVolumeList(
-    Profile* profile,
-    std::vector<linked_ptr<extensions::api::file_system::Volume>>* result) {
+void FillVolumeList(Profile* profile,
+                    std::vector<linked_ptr<api::file_system::Volume>>* result) {
   using file_manager::VolumeManager;
   VolumeManager* const volume_manager = VolumeManager::Get(profile);
   DCHECK(volume_manager);
 
-  using extensions::api::file_system::Volume;
+  using api::file_system::Volume;
   const auto& volume_list = volume_manager->GetVolumeList();
   // Convert volume_list to result_volume_list.
   for (const auto& volume : volume_list) {
@@ -274,8 +273,6 @@ void FillVolumeList(
 
 }  // namespace
 
-namespace extensions {
-
 namespace file_system_api {
 
 base::FilePath GetLastChooseEntryDirectory(const ExtensionPrefs* prefs,
@@ -315,14 +312,13 @@ void DispatchVolumeListChangeEvent(Profile* profile) {
   if (!event_router)  // Possible on shutdown.
     return;
 
-  extensions::ExtensionRegistry* const registry =
-      extensions::ExtensionRegistry::Get(profile);
+  ExtensionRegistry* const registry = ExtensionRegistry::Get(profile);
   if (!registry)  // Possible on shutdown.
     return;
 
   ConsentProviderDelegate consent_provider_delegate(profile, nullptr);
   ConsentProvider consent_provider(&consent_provider_delegate);
-  extensions::api::file_system::VolumeListChangedEvent event_args;
+  api::file_system::VolumeListChangedEvent event_args;
   FillVolumeList(profile, &event_args.volumes);
   for (const auto& extension : registry->enabled_extensions()) {
     if (!consent_provider.IsGrantable(*extension.get()))
@@ -330,10 +326,9 @@ void DispatchVolumeListChangeEvent(Profile* profile) {
     event_router->DispatchEventToExtension(
         extension->id(),
         make_scoped_ptr(new Event(
-            events::UNKNOWN,
-            extensions::api::file_system::OnVolumeListChanged::kEventName,
-            extensions::api::file_system::OnVolumeListChanged::Create(
-                event_args))));
+            events::FILE_SYSTEM_ON_VOLUME_LIST_CHANGED,
+            api::file_system::OnVolumeListChanged::kEventName,
+            api::file_system::OnVolumeListChanged::Create(event_args))));
   }
 }
 
@@ -346,7 +341,7 @@ ConsentProvider::~ConsentProvider() {
 }
 
 void ConsentProvider::RequestConsent(
-    const extensions::Extension& extension,
+    const Extension& extension,
     const base::WeakPtr<file_manager::Volume>& volume,
     bool writable,
     const ConsentCallback& callback) {
@@ -424,7 +419,7 @@ void ConsentProviderDelegate::SetAutoDialogButtonForTest(
 }
 
 void ConsentProviderDelegate::ShowDialog(
-    const extensions::Extension& extension,
+    const Extension& extension,
     const base::WeakPtr<file_manager::Volume>& volume,
     bool writable,
     const file_system_api::ConsentProvider::ShowDialogCallback& callback) {
@@ -456,22 +451,21 @@ void ConsentProviderDelegate::ShowDialog(
 }
 
 void ConsentProviderDelegate::ShowNotification(
-    const extensions::Extension& extension,
+    const Extension& extension,
     const base::WeakPtr<file_manager::Volume>& volume,
     bool writable) {
   RequestFileSystemNotification::ShowAutoGrantedNotification(
       profile_, extension, volume, writable);
 }
 
-bool ConsentProviderDelegate::IsAutoLaunched(
-    const extensions::Extension& extension) {
+bool ConsentProviderDelegate::IsAutoLaunched(const Extension& extension) {
   chromeos::KioskAppManager::App app_info;
   return chromeos::KioskAppManager::Get()->GetApp(extension.id(), &app_info) &&
          app_info.was_auto_launched_with_zero_delay;
 }
 
 bool ConsentProviderDelegate::IsWhitelistedComponent(
-    const extensions::Extension& extension) {
+    const Extension& extension) {
   for (const auto& whitelisted_id : kRequestFileSystemComponentWhitelist) {
     if (extension.id().compare(whitelisted_id) == 0)
       return true;
@@ -1145,8 +1139,7 @@ bool FileSystemRetainEntryFunction::RunAsync() {
     if (!storage::CrackIsolatedFileSystemName(filesystem_name, &filesystem_id))
       return false;
 
-    const GURL site =
-        extensions::util::GetSiteForExtensionId(extension_id(), GetProfile());
+    const GURL site = util::GetSiteForExtensionId(extension_id(), GetProfile());
     storage::FileSystemContext* const context =
         content::BrowserContext::GetStoragePartitionForSite(GetProfile(), site)
             ->GetFileSystemContext();
@@ -1250,7 +1243,7 @@ bool FileSystemGetObservedEntriesFunction::RunSync() {
 
 #if !defined(OS_CHROMEOS)
 ExtensionFunction::ResponseAction FileSystemRequestFileSystemFunction::Run() {
-  using extensions::api::file_system::RequestFileSystem::Params;
+  using api::file_system::RequestFileSystem::Params;
   const scoped_ptr<Params> params(Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params);
 
@@ -1272,7 +1265,7 @@ FileSystemRequestFileSystemFunction::~FileSystemRequestFileSystemFunction() {
 }
 
 ExtensionFunction::ResponseAction FileSystemRequestFileSystemFunction::Run() {
-  using extensions::api::file_system::RequestFileSystem::Params;
+  using api::file_system::RequestFileSystem::Params;
   const scoped_ptr<Params> params(Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params);
 
@@ -1303,8 +1296,8 @@ ExtensionFunction::ResponseAction FileSystemRequestFileSystemFunction::Run() {
   if (!volume.get())
     return RespondNow(Error(kVolumeNotFoundError));
 
-  const GURL site = extensions::util::GetSiteForExtensionId(
-      extension_id(), chrome_details_.GetProfile());
+  const GURL site =
+      util::GetSiteForExtensionId(extension_id(), chrome_details_.GetProfile());
   scoped_refptr<storage::FileSystemContext> file_system_context =
       content::BrowserContext::GetStoragePartitionForSite(
           chrome_details_.GetProfile(), site)->GetFileSystemContext();
@@ -1354,8 +1347,8 @@ void FileSystemRequestFileSystemFunction::OnConsentReceived(
     return;
   }
 
-  const GURL site = extensions::util::GetSiteForExtensionId(
-      extension_id(), chrome_details_.GetProfile());
+  const GURL site =
+      util::GetSiteForExtensionId(extension_id(), chrome_details_.GetProfile());
   scoped_refptr<storage::FileSystemContext> file_system_context =
       content::BrowserContext::GetStoragePartitionForSite(
           chrome_details_.GetProfile(), site)->GetFileSystemContext();
@@ -1376,8 +1369,8 @@ void FileSystemRequestFileSystemFunction::OnConsentReceived(
 
   const storage::FileSystemURL original_url =
       file_system_context->CreateCrackedFileSystemURL(
-          GURL(std::string(extensions::kExtensionScheme) +
-               url::kStandardSchemeSeparator + extension_id()),
+          GURL(std::string(kExtensionScheme) + url::kStandardSchemeSeparator +
+               extension_id()),
           storage::kFileSystemTypeExternal, virtual_path);
 
   // Set a fixed register name, as the automatic one would leak the mount point
@@ -1445,12 +1438,12 @@ ExtensionFunction::ResponseAction FileSystemGetVolumeListFunction::Run() {
 
   if (!consent_provider.IsGrantable(*extension()))
     return RespondNow(Error(kNotSupportedOnNonKioskSessionError));
-  using extensions::api::file_system::Volume;
+  using api::file_system::Volume;
   std::vector<linked_ptr<Volume>> result_volume_list;
   FillVolumeList(chrome_details_.GetProfile(), &result_volume_list);
 
   return RespondNow(
-      ArgumentList(extensions::api::file_system::GetVolumeList::Results::Create(
+      ArgumentList(api::file_system::GetVolumeList::Results::Create(
                        result_volume_list).Pass()));
 }
 #endif
diff --git a/chrome/browser/extensions/api/file_system/file_system_api.h b/chrome/browser/extensions/api/file_system/file_system_api.h
index 2f8d446..6a2ca2c 100644
--- a/chrome/browser/extensions/api/file_system/file_system_api.h
+++ b/chrome/browser/extensions/api/file_system/file_system_api.h
@@ -64,23 +64,22 @@ class ConsentProvider {
   class DelegateInterface {
    public:
     // Shows a dialog for granting permissions.
-    virtual void ShowDialog(const extensions::Extension& extension,
+    virtual void ShowDialog(const Extension& extension,
                             const base::WeakPtr<file_manager::Volume>& volume,
                             bool writable,
                             const ShowDialogCallback& callback) = 0;
 
     // Shows a notification about permissions automatically granted access.
     virtual void ShowNotification(
-        const extensions::Extension& extension,
+        const Extension& extension,
         const base::WeakPtr<file_manager::Volume>& volume,
         bool writable) = 0;
 
     // Checks if the extension was launched in auto-launch kiosk mode.
-    virtual bool IsAutoLaunched(const extensions::Extension& extension) = 0;
+    virtual bool IsAutoLaunched(const Extension& extension) = 0;
 
     // Checks if the extension is a whitelisted component extension or app.
-    virtual bool IsWhitelistedComponent(
-        const extensions::Extension& extension) = 0;
+    virtual bool IsWhitelistedComponent(const Extension& extension) = 0;
   };
 
   explicit ConsentProvider(DelegateInterface* delegate);
@@ -89,13 +88,13 @@ class ConsentProvider {
   // Requests consent for granting |writable| permissions to the |volume|
   // volume by the |extension|. Must be called only if the extension is
   // grantable, which can be checked with IsGrantable().
-  void RequestConsent(const extensions::Extension& extension,
+  void RequestConsent(const Extension& extension,
                       const base::WeakPtr<file_manager::Volume>& volume,
                       bool writable,
                       const ConsentCallback& callback);
 
   // Checks whether the |extension| can be granted access.
-  bool IsGrantable(const extensions::Extension& extension);
+  bool IsGrantable(const Extension& extension);
 
  private:
   DelegateInterface* const delegate_;
@@ -123,16 +122,16 @@ class ConsentProviderDelegate : public ConsentProvider::DelegateInterface {
   static void SetAutoDialogButtonForTest(ui::DialogButton button);
 
   // ConsentProvider::DelegateInterface overrides:
-  void ShowDialog(const extensions::Extension& extension,
+  void ShowDialog(const Extension& extension,
                   const base::WeakPtr<file_manager::Volume>& volume,
                   bool writable,
                   const file_system_api::ConsentProvider::ShowDialogCallback&
                       callback) override;
-  void ShowNotification(const extensions::Extension& extension,
+  void ShowNotification(const Extension& extension,
                         const base::WeakPtr<file_manager::Volume>& volume,
                         bool writable) override;
-  bool IsAutoLaunched(const extensions::Extension& extension) override;
-  bool IsWhitelistedComponent(const extensions::Extension& extension) override;
+  bool IsAutoLaunched(const Extension& extension) override;
+  bool IsWhitelistedComponent(const Extension& extension) override;
 
   Profile* const profile_;
   content::RenderFrameHost* const host_;
@@ -238,8 +237,7 @@ class FileSystemChooseEntryFunction : public FileSystemEntryFunction {
                                                     const base::FilePath& path);
   DECLARE_EXTENSION_FUNCTION("fileSystem.chooseEntry", FILESYSTEM_CHOOSEENTRY)
 
-  typedef std::vector<linked_ptr<extensions::api::file_system::AcceptOption> >
-      AcceptOptions;
+  typedef std::vector<linked_ptr<api::file_system::AcceptOption>> AcceptOptions;
 
   static void BuildFileTypeInfo(
       ui::SelectFileDialog::FileTypeInfo* file_type_info,
diff --git a/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc b/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
index 5002c76..4a39a56 100644
--- a/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
+++ b/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
@@ -57,15 +57,15 @@ scoped_ptr<Event> MakeDeviceStateChangedEvent(
   scoped_ptr<base::ListValue> params =
       gcd_private::OnDeviceStateChanged::Create(device);
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, gcd_private::OnDeviceStateChanged::kEventName,
-                params.Pass()));
+      new Event(events::GCD_PRIVATE_ON_DEVICE_STATE_CHANGED,
+                gcd_private::OnDeviceStateChanged::kEventName, params.Pass()));
   return event.Pass();
 }
 
 scoped_ptr<Event> MakeDeviceRemovedEvent(const std::string& device) {
   scoped_ptr<base::ListValue> params =
       gcd_private::OnDeviceRemoved::Create(device);
-  scoped_ptr<Event> event(new Event(events::UNKNOWN,
+  scoped_ptr<Event> event(new Event(events::GCD_PRIVATE_ON_DEVICE_REMOVED,
                                     gcd_private::OnDeviceRemoved::kEventName,
                                     params.Pass()));
   return event.Pass();
diff --git a/chrome/browser/extensions/api/gcm/gcm_api.cc b/chrome/browser/extensions/api/gcm/gcm_api.cc
index 714f3ee..ba76151 100644
--- a/chrome/browser/extensions/api/gcm/gcm_api.cc
+++ b/chrome/browser/extensions/api/gcm/gcm_api.cc
@@ -215,15 +215,15 @@ void GcmJsEventRouter::OnMessage(const std::string& app_id,
     message_arg.collapse_key.reset(new std::string(message.collapse_key));
 
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, api::gcm::OnMessage::kEventName,
+      new Event(events::GCM_ON_MESSAGE, api::gcm::OnMessage::kEventName,
                 api::gcm::OnMessage::Create(message_arg).Pass(), profile_));
   EventRouter::Get(profile_)->DispatchEventToExtension(app_id, event.Pass());
 }
 
 void GcmJsEventRouter::OnMessagesDeleted(const std::string& app_id) {
-  scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, api::gcm::OnMessagesDeleted::kEventName,
-                api::gcm::OnMessagesDeleted::Create().Pass(), profile_));
+  scoped_ptr<Event> event(new Event(
+      events::GCM_ON_MESSAGES_DELETED, api::gcm::OnMessagesDeleted::kEventName,
+      api::gcm::OnMessagesDeleted::Create().Pass(), profile_));
   EventRouter::Get(profile_)->DispatchEventToExtension(app_id, event.Pass());
 }
 
@@ -236,7 +236,7 @@ void GcmJsEventRouter::OnSendError(
   error.details.additional_properties = send_error_details.additional_data;
 
   scoped_ptr<Event> event(
-      new Event(events::UNKNOWN, api::gcm::OnSendError::kEventName,
+      new Event(events::GCM_ON_SEND_ERROR, api::gcm::OnSendError::kEventName,
                 api::gcm::OnSendError::Create(error).Pass(), profile_));
   EventRouter::Get(profile_)->DispatchEventToExtension(app_id, event.Pass());
 }
diff --git a/chrome/browser/extensions/api/history/history_api.cc b/chrome/browser/extensions/api/history/history_api.cc
index 47cc8b5..c267fe9 100644
--- a/chrome/browser/extensions/api/history/history_api.cc
+++ b/chrome/browser/extensions/api/history/history_api.cc
@@ -36,7 +36,6 @@ namespace extensions {
 
 using api::history::HistoryItem;
 using api::history::VisitItem;
-using extensions::ActivityLog;
 
 typedef std::vector<linked_ptr<api::history::HistoryItem> >
     HistoryItemList;
@@ -147,7 +146,8 @@ void HistoryEventRouter::OnURLVisited(history::HistoryService* history_service,
                                       base::Time visit_time) {
   scoped_ptr<HistoryItem> history_item = GetHistoryItem(row);
   scoped_ptr<base::ListValue> args = OnVisited::Create(*history_item);
-  DispatchEvent(profile_, api::history::OnVisited::kEventName, args.Pass());
+  DispatchEvent(profile_, events::HISTORY_ON_VISITED,
+                api::history::OnVisited::kEventName, args.Pass());
 }
 
 void HistoryEventRouter::OnURLsDeleted(history::HistoryService* history_service,
@@ -164,19 +164,19 @@ void HistoryEventRouter::OnURLsDeleted(history::HistoryService* history_service,
   removed.urls.reset(urls);
 
   scoped_ptr<base::ListValue> args = OnVisitRemoved::Create(removed);
-  DispatchEvent(profile_, api::history::OnVisitRemoved::kEventName,
-                args.Pass());
+  DispatchEvent(profile_, events::HISTORY_ON_VISIT_REMOVED,
+                api::history::OnVisitRemoved::kEventName, args.Pass());
 }
 
-void HistoryEventRouter::DispatchEvent(
-    Profile* profile,
-    const std::string& event_name,
-    scoped_ptr<base::ListValue> event_args) {
-  if (profile && extensions::EventRouter::Get(profile)) {
-    scoped_ptr<extensions::Event> event(new extensions::Event(
-        extensions::events::UNKNOWN, event_name, event_args.Pass()));
+void HistoryEventRouter::DispatchEvent(Profile* profile,
+                                       events::HistogramValue histogram_value,
+                                       const std::string& event_name,
+                                       scoped_ptr<base::ListValue> event_args) {
+  if (profile && EventRouter::Get(profile)) {
+    scoped_ptr<Event> event(
+        new Event(histogram_value, event_name, event_args.Pass()));
     event->restrict_to_browser_context = profile;
-    extensions::EventRouter::Get(profile)->BroadcastEvent(event.Pass());
+    EventRouter::Get(profile)->BroadcastEvent(event.Pass());
   }
 }
 
diff --git a/chrome/browser/extensions/api/history/history_api.h b/chrome/browser/extensions/api/history/history_api.h
index 0df5980..2335dbd 100644
--- a/chrome/browser/extensions/api/history/history_api.h
+++ b/chrome/browser/extensions/api/history/history_api.h
@@ -49,6 +49,7 @@ class HistoryEventRouter : public history::HistoryServiceObserver {
                      const std::set<GURL>& favicon_urls) override;
 
   void DispatchEvent(Profile* profile,
+                     events::HistogramValue histogram_value,
                      const std::string& event_name,
                      scoped_ptr<base::ListValue> event_args);
 
diff --git a/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc b/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
index 66162645..4e20c4f 100644
--- a/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
+++ b/chrome/browser/extensions/api/hotword_private/hotword_private_api.cc
@@ -75,53 +75,67 @@ void HotwordPrivateEventService::OnEnabledChanged(
          pref_name == std::string(prefs::kHotwordAlwaysOnSearchEnabled) ||
          pref_name == std::string(
              hotword_internal::kHotwordTrainingEnabled));
-  SignalEvent(OnEnabledChanged::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_ENABLED_CHANGED,
+              OnEnabledChanged::kEventName);
 }
 
 void HotwordPrivateEventService::OnHotwordSessionRequested() {
-  SignalEvent(api::hotword_private::OnHotwordSessionRequested::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_HOTWORD_SESSION_REQUESTED,
+              api::hotword_private::OnHotwordSessionRequested::kEventName);
 }
 
 void HotwordPrivateEventService::OnHotwordSessionStopped() {
-  SignalEvent(api::hotword_private::OnHotwordSessionStopped::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_HOTWORD_SESSION_STOPPED,
+              api::hotword_private::OnHotwordSessionStopped::kEventName);
 }
 
 void HotwordPrivateEventService::OnFinalizeSpeakerModel() {
-  SignalEvent(api::hotword_private::OnFinalizeSpeakerModel::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_FINALIZE_SPEAKER_MODEL,
+              api::hotword_private::OnFinalizeSpeakerModel::kEventName);
 }
 
 void HotwordPrivateEventService::OnSpeakerModelSaved() {
-  SignalEvent(api::hotword_private::OnSpeakerModelSaved::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_SPEAKER_MODEL_SAVED,
+              api::hotword_private::OnSpeakerModelSaved::kEventName);
 }
 
 void HotwordPrivateEventService::OnHotwordTriggered() {
-  SignalEvent(api::hotword_private::OnHotwordTriggered::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_HOTWORD_TRIGGERED,
+              api::hotword_private::OnHotwordTriggered::kEventName);
 }
 
 void HotwordPrivateEventService::OnDeleteSpeakerModel() {
-  SignalEvent(api::hotword_private::OnDeleteSpeakerModel::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_DELETE_SPEAKER_MODEL,
+              api::hotword_private::OnDeleteSpeakerModel::kEventName);
 }
 
 void HotwordPrivateEventService::OnSpeakerModelExists() {
-  SignalEvent(api::hotword_private::OnSpeakerModelExists::kEventName);
+  SignalEvent(events::HOTWORD_PRIVATE_ON_SPEAKER_MODEL_EXISTS,
+              api::hotword_private::OnSpeakerModelExists::kEventName);
 }
 
 void HotwordPrivateEventService::OnMicrophoneStateChanged(bool enabled) {
-  SignalEvent(api::hotword_private::OnMicrophoneStateChanged::kEventName,
+  SignalEvent(events::HOTWORD_PRIVATE_ON_MICROPHONE_STATE_CHANGED,
+              api::hotword_private::OnMicrophoneStateChanged::kEventName,
               api::hotword_private::OnMicrophoneStateChanged::Create(enabled));
 }
 
-void HotwordPrivateEventService::SignalEvent(const std::string& event_name) {
-  SignalEvent(event_name, make_scoped_ptr(new base::ListValue()));
+void HotwordPrivateEventService::SignalEvent(
+    events::HistogramValue histogram_value,
+    const std::string& event_name) {
+  SignalEvent(histogram_value, event_name,
+              make_scoped_ptr(new base::ListValue()));
 }
 
-void HotwordPrivateEventService::SignalEvent(const std::string& event_name,
-                                             scoped_ptr<base::ListValue> args) {
+void HotwordPrivateEventService::SignalEvent(
+    events::HistogramValue histogram_value,
+    const std::string& event_name,
+    scoped_ptr<base::ListValue> args) {
   EventRouter* router = EventRouter::Get(profile_);
   if (!router || !router->HasEventListener(event_name))
     return;
 
-  scoped_ptr<Event> event(new Event(events::UNKNOWN, event_name, args.Pass()));
+  scoped_ptr<Event> event(new Event(histogram_value, event_name, args.Pass()));
   router->BroadcastEvent(event.Pass());
 }
 
diff --git a/chrome/browser/extensions/api/hotword_private/hotword_private_api.h b/chrome/browser/extensions/api/hotword_private/hotword_private_api.h
index d25b5b7..bf2d0a8 100644
--- a/chrome/browser/extensions/api/hotword_private/hotword_private_api.h
+++ b/chrome/browser/extensions/api/hotword_private/hotword_private_api.h
@@ -10,6 +10,7 @@
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/common/extensions/api/hotword_private.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
+#include "extensions/browser/extension_event_histogram_value.h"
 
 class Profile;
 
@@ -49,8 +50,10 @@ class HotwordPrivateEventService : public BrowserContextKeyedAPI {
  private:
   friend class BrowserContextKeyedAPIFactory<HotwordPrivateEventService>;
 
-  void SignalEvent(const std::string& event_name);
-  void SignalEvent(const std::string& event_name,
+  void SignalEvent(events::HistogramValue histogram_value,
+                   const std::string& event_name);
+  void SignalEvent(events::HistogramValue histogram_value,
+                   const std::string& event_name,
                    scoped_ptr<base::ListValue> args);
 
   Profile* profile_;