Plumb default zoom level change events to zoom icon in location bar.

At present, a change in the default zoom level does not immediately
update the zoom icon in the location bar. E.g. if we change the zoom
level of chrome://settings to 90% (causing the zoom icon to display a
'-' symbol), then change the default zoom level to be 75%, the icon
should switch to show '+'.

This CL adds an event subscription to the ZoomEventManager in order
to receive notifications about default zoom level changes.

BUG=451349

Review URL: https://codereview.chromium.org/897513003

Cr-Commit-Position: refs/heads/master@{#314568}

chrome/browser/ui/views/location_bar/location_bar_view.cc

@@ -64,6 +64,7 @@
 #include "components/search_engines/template_url_service.h"
 #include "components/translate/core/browser/language_state.h"
 #include "components/ui/zoom/zoom_controller.h"
+#include "components/ui/zoom/zoom_event_manager.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/extension_registry.h"
@@ -193,6 +194,9 @@ LocationBarView::LocationBarView(Browser* browser,
 
   if (browser_)
     browser_->search_model()->AddObserver(this);
+
+  ui_zoom::ZoomEventManager::GetForBrowserContext(profile)
+      ->AddZoomEventManagerObserver(this);
 }
 
 LocationBarView::~LocationBarView() {
@@ -200,6 +204,9 @@ LocationBarView::~LocationBarView() {
     template_url_service_->RemoveObserver(this);
   if (browser_)
     browser_->search_model()->RemoveObserver(this);
+
+  ui_zoom::ZoomEventManager::GetForBrowserContext(profile())
+      ->RemoveZoomEventManagerObserver(this);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1153,6 +1160,10 @@ bool LocationBarView::RefreshZoomView() {
   return was_visible != zoom_view_->visible();
 }
 
+void LocationBarView::OnDefaultZoomLevelChanged() {
+  RefreshZoomView();
+}
+
 void LocationBarView::RefreshTranslateIcon() {
   if (!TranslateService::IsTranslateBubbleEnabled())
     return;

chrome/browser/ui/views/location_bar/location_bar_view.h

@@ -20,6 +20,7 @@
 #include "chrome/browser/ui/views/extensions/extension_popup.h"
 #include "chrome/browser/ui/views/omnibox/omnibox_view_views.h"
 #include "components/search_engines/template_url_service_observer.h"
+#include "components/ui/zoom/zoom_event_manager_observer.h"
 #include "ui/gfx/animation/animation_delegate.h"
 #include "ui/gfx/font.h"
 #include "ui/gfx/geometry/rect.h"
@@ -83,7 +84,8 @@ class LocationBarView : public LocationBar,
                         public DropdownBarHostDelegate,
                         public gfx::AnimationDelegate,
                         public TemplateURLServiceObserver,
-                        public SearchModelObserver {
+                        public SearchModelObserver,
+                        public ui_zoom::ZoomEventManagerObserver {
  public:
   // The location bar view's class name.
   static const char kViewClassName[];
@@ -259,6 +261,10 @@ class LocationBarView : public LocationBar,
   ToolbarModel* GetToolbarModel() override;
   content::WebContents* GetWebContents() override;
 
+  // ZoomEventManagerObserver:
+  // Updates the view for the zoom icon when default zoom levels change.
+  void OnDefaultZoomLevelChanged() override;
+
   // Thickness of the edges of the omnibox background images, in normal mode.
   static const int kNormalEdgeThickness;
   // The same, but for popup mode.

chrome/browser/ui/zoom/chrome_zoom_level_prefs.cc

@@ -71,6 +71,8 @@ void ChromeZoomLevelPrefs::SetDefaultZoomLevelPref(double level) {
   // set this manually.
   host_zoom_map_->SetDefaultZoomLevel(level);
   default_zoom_changed_callbacks_.Notify();
+  if (zoom_event_manager_)
+    zoom_event_manager_->OnDefaultZoomLevelChanged();
 }
 
 double ChromeZoomLevelPrefs::GetDefaultZoomLevelPref() const {

components/ui/zoom/BUILD.gn

@@ -12,6 +12,7 @@ static_library("ui_zoom") {
     "zoom_controller.h",
     "zoom_event_manager.cc",
     "zoom_event_manager.h",
+    "zoom_event_manager_observer.h",
     "zoom_observer.h",
   ]
 

components/ui/zoom/zoom_event_manager.cc

@@ -4,6 +4,7 @@
 
 #include "components/ui/zoom/zoom_event_manager.h"
 
+#include "components/ui/zoom/zoom_event_manager_observer.h"
 #include "content/public/browser/browser_context.h"
 
 namespace {
@@ -37,4 +38,19 @@ ZoomEventManager::AddZoomLevelChangedCallback(
   return zoom_level_changed_callbacks_.Add(callback);
 }
 
+void ZoomEventManager::OnDefaultZoomLevelChanged() {
+  FOR_EACH_OBSERVER(ZoomEventManagerObserver, observers_,
+                    OnDefaultZoomLevelChanged());
+}
+
+void ZoomEventManager::AddZoomEventManagerObserver(
+    ZoomEventManagerObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void ZoomEventManager::RemoveZoomEventManagerObserver(
+    ZoomEventManagerObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 }  // namespace ui_zoom

components/ui/zoom/zoom_event_manager.h

@@ -7,6 +7,7 @@
 
 #include "base/callback_list.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "base/supports_user_data.h"
 #include "content/public/browser/host_zoom_map.h"
 
@@ -16,6 +17,8 @@ class BrowserContext;
 
 namespace ui_zoom {
 
+class ZoomEventManagerObserver;
+
 // This class serves as a target for event notifications from all ZoomController
 // objects. Classes that need to know about browser-specific zoom events (e.g.
 // manual-mode zoom) should subscribe here.
@@ -34,9 +37,19 @@ class ZoomEventManager : public base::SupportsUserData::Data {
   void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
 
   // Add and remove zoom level changed callbacks.
+  // TODO(wjmaclean): Convert this callback mechanism to use
+  // ZoomEventManagerObserver instead.
   scoped_ptr<content::HostZoomMap::Subscription> AddZoomLevelChangedCallback(
       const content::HostZoomMap::ZoomLevelChangedCallback& callback);
 
+  // Called by ZoomLevelDelegates when changes are made to the default zoom
+  // level for their associated HostZoomMap.
+  void OnDefaultZoomLevelChanged();
+
+  // Add and remove observers.
+  void AddZoomEventManagerObserver(ZoomEventManagerObserver* observer);
+  void RemoveZoomEventManagerObserver(ZoomEventManagerObserver* observer);
+
   // Get a weak ptr to be used by clients who may themselves be UserData for
   // the context, since the order of destruction is undefined between the client
   // and this class.
@@ -47,6 +60,7 @@ class ZoomEventManager : public base::SupportsUserData::Data {
  private:
   base::CallbackList<void(const content::HostZoomMap::ZoomLevelChange&)>
       zoom_level_changed_callbacks_;
+  ObserverList<ZoomEventManagerObserver> observers_;
   base::WeakPtrFactory<ZoomEventManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomEventManager);

components/ui/zoom/zoom_event_manager_observer.h

+// Copyright 2015 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 COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_OBSERVER_H_
+#define COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_OBSERVER_H_
+
+namespace ui_zoom {
+
+class ZoomEventManagerObserver {
+ public:
+  // TODO(wjmaclean): convert existing ZoomLevelChangedCallbacks to be
+  // observers.
+  virtual void OnZoomLevelChanged() {}
+  virtual void OnDefaultZoomLevelChanged() {}
+
+ protected:
+  virtual ~ZoomEventManagerObserver() {}
+};
+
+}  // namespace ui_zoom
+
+#endif  // COMPONENTS_UI_ZOOM_ZOOM_EVENT_MANAGER_OBSERVER_H_

components/ui_zoom.gypi

@@ -27,6 +27,7 @@
         'ui/zoom/zoom_controller.h',
         'ui/zoom/zoom_event_manager.cc',
         'ui/zoom/zoom_event_manager.h',
+        'ui/zoom/zoom_event_manager_observer.h',
         'ui/zoom/zoom_observer.h'
       ],
     }