[Win] Don't crash when updating tooltip and the ClientView hasn't been added to the view hierarchy.

ui/views/widget/tooltip_manager_aura.cc

 // Copyright (c) 2012 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 "ui/views/widget/tooltip_manager_aura.h"
 
 #include "base/logging.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_tree_host.h"
@@ skipping 72 matching lines @@
 
 int TooltipManagerAura::GetMaxWidth(const gfx::Point& point,
                                     aura::Window* context) const {
   return aura::client::GetTooltipClient(context->GetRootWindow())->
       GetMaxWidth(point, context);
 }
 
 void TooltipManagerAura::UpdateTooltip() {
   aura::Window* root_window = GetWindow()->GetRootWindow();
   if (aura::client::GetTooltipClient(root_window)) {
+    if (!widget_->IsVisible()) {
+      UpdateTooltipForTarget(NULL, gfx::Point(), root_window);
+      return;
+    }
     gfx::Point view_point =
         root_window->GetHost()->dispatcher()->GetLastMouseLocationInRoot();
     aura::Window::ConvertPointToTarget(root_window, GetWindow(), &view_point);
     View* view = GetViewUnderPoint(view_point);
     UpdateTooltipForTarget(view, view_point, root_window);
   }
 }
 
 void TooltipManagerAura::TooltipTextChanged(View* view)  {
   aura::Window* root_window = GetWindow()->GetRootWindow();
@@ skipping 33 matching lines @@
   aura::client::SetTooltipId(GetWindow(), target);
 
   aura::client::GetTooltipClient(root_window)->UpdateTooltip(GetWindow());
 }
 
 aura::Window* TooltipManagerAura::GetWindow() {
   return widget_->GetNativeView();
 }
 
 }  // namespace views.