Remove TransparentActivateWindowButton from Overview Mode

ash/wm/workspace/workspace_event_handler.cc

Index: ash/wm/workspace/workspace_event_handler.cc
diff --git a/ash/wm/workspace/workspace_event_handler.cc b/ash/wm/workspace/workspace_event_handler.cc
index afd017bb0e8bacea4a2de7bffe13d8844074a046..25d9ee0aa58227db9411c27f1058e195b864b713 100644
--- a/ash/wm/workspace/workspace_event_handler.cc
+++ b/ash/wm/workspace/workspace_event_handler.cc
@@ -24,6 +24,10 @@ WorkspaceEventHandler::~WorkspaceEventHandler() {
 
 void WorkspaceEventHandler::OnMouseEvent(ui::MouseEvent* event) {
   aura::Window* target = static_cast<aura::Window*>(event->target());
+
+  if (!target->delegate())

[Nina, 2015/01/09 15:43:49]

Without the change, this code would crash if the user clicked, switched to
overview and quickly clicked again.

+    return;
+
   if (event->type() == ui::ET_MOUSE_PRESSED &&
       event->IsOnlyLeftMouseButton() &&
       ((event->flags() &
@@ -82,6 +86,10 @@ void WorkspaceEventHandler::OnGestureEvent(ui::GestureEvent* event) {
     return;
 
   aura::Window* target = static_cast<aura::Window*>(event->target());
+
+  if (!target->delegate())
+    return;
+
   int previous_target_component = click_component_;
   click_component_ = target->delegate()->
       GetNonClientComponent(event->location());