Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/aura/wm_shelf_aura.cc

 // Copyright 2016 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 "ash/aura/wm_shelf_aura.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shelf/wm_shelf_observer.h"
 #include "ash/common/wm_window.h"
 #include "ash/shelf/shelf.h"
@@ skipping 26 matching lines @@
   }
 
   ResetShelfLayoutManager();
 }
 
 // static
 Shelf* WmShelfAura::GetShelf(WmShelf* shelf) {
   return static_cast<WmShelfAura*>(shelf)->shelf_;
 }
 
+void WmShelfAura::AddObserver(WmShelfObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void WmShelfAura::RemoveObserver(WmShelfObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 void WmShelfAura::ResetShelfLayoutManager() {
   if (!shelf_layout_manager_)
     return;
   shelf_layout_manager_->RemoveObserver(this);
   shelf_layout_manager_ = nullptr;
 }
 
 WmWindow* WmShelfAura::GetWindow() {
   return WmWindowAura::Get(shelf_->shelf_widget()->GetNativeView());
 }
@@ skipping 29 matching lines @@
 
 void WmShelfAura::UpdateIconPositionForWindow(WmWindow* window) {
   shelf_->UpdateIconPositionForWindow(WmWindowAura::GetAuraWindow(window));
 }
 
 gfx::Rect WmShelfAura::GetScreenBoundsOfItemIconForWindow(WmWindow* window) {
   return shelf_->GetScreenBoundsOfItemIconForWindow(
       WmWindowAura::GetAuraWindow(window));
 }
 
-void WmShelfAura::AddObserver(WmShelfObserver* observer) {
-  observers_.AddObserver(observer);
-}
-
-void WmShelfAura::RemoveObserver(WmShelfObserver* observer) {
-  observers_.RemoveObserver(observer);
-}
-
 void WmShelfAura::WillDeleteShelfLayoutManager() {
   ResetShelfLayoutManager();
 }
 
 void WmShelfAura::OnBackgroundUpdated(
     ShelfBackgroundType background_type,
     BackgroundAnimatorChangeType change_type) {
+  if (background_type == GetBackgroundType())

[James Cook, 2016/06/14 17:50:00]

This might change when the observer fires compared to the behavior in
ShelfLayoutManager::UpdateShelfBackground(), affecting
DockedWindowLayoutManager. Are you sure this is safe?

[bruthig, 2016/07/26 19:50:01]

It most definitely changes when the WmShelfObserver is notified ;)  Before this
change the WmShelfObserver's could get spammed with notifications even when the
|background_type| didn't change.  (e.g.
ShelfLayoutManager::SetWindowOverlapsShelf() gets called for each mouse drag
event)  This is most definitely sub-optimal.

I've renamed WmShelfObserver::OnBackgroundUpdated() as OnBackgroundChanged() to
be more clear that it actually changed.  And the only two overrides of this are
in
ShelfBackgroundAnimator and DockedBackgroundWidget which only need to know if
the background type actually changed.

IMO the ShelfLayoutManager should only notify it's observers when the background
type has changed as well.  But this is not a straight forward change and it's
unclear if some observers require the current spammy behavior. However, I could
add a TODO if you'd like?

[James Cook, 2016/07/27 00:30:38]

Yes, please TODO it.

+    return;
   FOR_EACH_OBSERVER(WmShelfObserver, observers_,
                     OnBackgroundUpdated(background_type, change_type));
 }
 
 void WmShelfAura::WillChangeVisibilityState(ShelfVisibilityState new_state) {
   FOR_EACH_OBSERVER(WmShelfObserver, observers_,
                     WillChangeVisibilityState(new_state));
 }
 
 void WmShelfAura::OnShelfIconPositionsChanged() {
   FOR_EACH_OBSERVER(WmShelfObserver, observers_, OnShelfIconPositionsChanged());
 }
 
 }  // namespace ash