Unified: Ignore swipe collapsing in detailed views

UnifiedSystemTray can be expanded or collapsed by touch gestures, but
it's confusing that it's also possible when a detailed view is shown.

TEST=manual
BUG=none

Change-Id: Iac81bbb645036560aa01c43bd86de735e3e904dc
Reviewed-on: https://chromium-review.googlesource.com/c/1352088
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612080}

ash/system/unified/unified_system_tray_controller.cc

@@ -177,11 +177,17 @@ void UnifiedSystemTrayController::OnMessageCenterVisibilityUpdated() {
 }
 
 void UnifiedSystemTrayController::BeginDrag(const gfx::Point& location) {
+  // Ignore swipe collapsing when a detailed view is shown as it's confusing.
+  if (detailed_view_controller_)
+    return;
   drag_init_point_ = location;
   was_expanded_ = IsExpanded();
 }
 
 void UnifiedSystemTrayController::UpdateDrag(const gfx::Point& location) {
+  // Ignore swipe collapsing when a detailed view is shown as it's confusing.
+  if (detailed_view_controller_)
+    return;
   animation_->Reset(GetDragExpandedAmount(location));
   UpdateExpandedAmount();
 }
@@ -198,6 +204,9 @@ void UnifiedSystemTrayController::StartAnimation(bool expand) {
 }
 
 void UnifiedSystemTrayController::EndDrag(const gfx::Point& location) {
+  // Ignore swipe collapsing when a detailed view is shown as it's confusing.
+  if (detailed_view_controller_)
+    return;
   if (animation_->is_animating()) {
     // Prevent overwriting the state right after fling event
     return;
@@ -214,6 +223,9 @@ void UnifiedSystemTrayController::EndDrag(const gfx::Point& location) {
 }
 
 void UnifiedSystemTrayController::Fling(int velocity) {
+  // Ignore swipe collapsing when a detailed view is shown as it's confusing.
+  if (detailed_view_controller_)
+    return;
   // Expand when flinging up. Collapse otherwise.
   StartAnimation(velocity < 0);
 }