Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/app_list_button.cc

Index: ash/shelf/app_list_button.cc
diff --git a/ash/shelf/app_list_button.cc b/ash/shelf/app_list_button.cc
index 584d9d842d223fcaf91911116abcb9d32d96a0be..016773956839153d41bd44bdb00684bcfa74b77c 100644
--- a/ash/shelf/app_list_button.cc
+++ b/ash/shelf/app_list_button.cc
@@ -44,7 +44,7 @@ AppListButton::AppListButton(InkDropButtonListener* listener,
   DCHECK(listener_);
   DCHECK(shelf_view_);
   DCHECK(shelf_);
-
+  Shell::Get()->AddShellObserver(this);
   SetInkDropMode(InkDropMode::ON_NO_GESTURE_HANDLER);
   set_ink_drop_base_color(kShelfInkDropBaseColor);
   set_ink_drop_visible_opacity(kShelfInkDropVisibleOpacity);
@@ -55,7 +55,9 @@ AppListButton::AppListButton(InkDropButtonListener* listener,
   set_notify_action(CustomButton::NOTIFY_ON_PRESS);
 }
 
-AppListButton::~AppListButton() {}
+AppListButton::~AppListButton() {
+  Shell::Get()->RemoveShellObserver(this);
+}
 
 void AppListButton::OnAppListShown() {
   AnimateInkDrop(views::InkDropState::ACTIVATED, nullptr);
@@ -239,4 +241,16 @@ gfx::Point AppListButton::GetCenterPoint() const {
   }
 }
 
+void AppListButton::OnAppListVisibilityChanged(bool shown,
+                                               aura::Window* root_window) {
+  // If the AppList belonged to this shelf.

[msw, 2017/06/06 17:56:31]

nit: remove this comment, it's not a complete sentence, and the code conveys the
conditional well enough

[newcomer, 2017/06/06 23:26:27]

Done.

+  if (shelf_ == Shelf::ForWindow(root_window)) {

[xiyuan, 2017/06/06 16:50:18]

nit: reverse the condition and bail out early.

i.e.

if (shelf_ != Shelf::ForWindow(root_window))
  return;

...

[newcomer, 2017/06/06 17:12:56]

Done.

+    if (shown) {

[msw, 2017/06/06 17:56:31]

nit: no curlies needed for the nested if/else

[newcomer, 2017/06/06 23:26:27]

Done.

+      OnAppListShown();
+    } else {
+      OnAppListDismissed();
+    }
+  }
+}
+
 }  // namespace ash