Expand and collapse unified system tray by fling.

Bug: 850437
Test: manually tested
Change-Id: I36952d2962dc46ea0d9867fd89a7841d02fc1bbe
Reviewed-on: https://chromium-review.googlesource.com/1125583Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572531}

ash/system/unified/unified_system_tray_controller.cc

@@ -177,7 +177,22 @@ void UnifiedSystemTrayController::UpdateDrag(const gfx::Point& location) {
   UpdateExpandedAmount();
 }
 
+void UnifiedSystemTrayController::StartAnimation(bool expand) {
+  if (expand) {
+    animation_->Show();
+  } else {
+    // To animate to hidden state, first set SlideAnimation::IsShowing() to
+    // true.
+    animation_->Show();
+    animation_->Hide();
+  }
+}
+
 void UnifiedSystemTrayController::EndDrag(const gfx::Point& location) {
+  if (animation_->is_animating()) {
+    // Prevent overwriting the state right after fling event
+    return;
+  }
   bool expanded = GetDragExpandedAmount(location) > 0.5;
   if (was_expanded_ != expanded) {
     UMA_HISTOGRAM_ENUMERATION("ChromeOS.SystemTray.ToggleExpanded",
@@ -186,14 +201,12 @@ void UnifiedSystemTrayController::EndDrag(const gfx::Point& location) {
   }
 
   // If dragging is finished, animate to closer state.
-  if (expanded) {
-    animation_->Show();
-  } else {
-    // To animate to hidden state, first set SlideAnimation::IsShowing() to
-    // true.
-    animation_->Show();
-    animation_->Hide();
-  }
+  StartAnimation(expanded);
+}
+
+void UnifiedSystemTrayController::Fling(int velocity) {
+  // Expand when flinging up. Collapse otherwise.
+  StartAnimation(velocity < 0);
 }
 
 void UnifiedSystemTrayController::ShowUserChooserWidget() {

ash/system/unified/unified_system_tray_controller.h

@@ -65,6 +65,7 @@ class ASH_EXPORT UnifiedSystemTrayController : public gfx::AnimationDelegate {
   void BeginDrag(const gfx::Point& location);
   void UpdateDrag(const gfx::Point& location);
   void EndDrag(const gfx::Point& location);
+  void Fling(int velocity);
 
   // Show user selector popup widget. Called from the view.
   void ShowUserChooserWidget();
@@ -139,6 +140,9 @@ class ASH_EXPORT UnifiedSystemTrayController : public gfx::AnimationDelegate {
   // Return true if UnifiedSystemTray is expanded.
   bool IsExpanded() const;
 
+  // Starts animation to expand or collapse the bubble.
+  void StartAnimation(bool expand);
+
   // Model that stores UI specific variables. Unowned.
   UnifiedSystemTrayModel* const model_;
 

ash/system/unified/unified_system_tray_view.cc

@@ -248,6 +248,9 @@ void UnifiedSystemTrayView::OnGestureEvent(ui::GestureEvent* event) {
       controller_->EndDrag(screen_location);
       event->SetHandled();
       break;
+    case ui::ET_SCROLL_FLING_START:
+      controller_->Fling(event->details().velocity_y());
+      break;
     default:
       break;
   }