Fix mus-in-renderer scale factor crash

services/ui/public/cpp/window_tree_client.cc

 // Copyright 2014 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 "services/ui/public/cpp/window_tree_client.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 24 matching lines @@
 
 namespace ui {
 
 Id MakeTransportId(ClientSpecificId client_id, ClientSpecificId local_id) {
   return (client_id << 16) | local_id;
 }
 
 // Helper function to get the device_scale_factor() of the display::Display
 // with |display_id|.
 float ScaleFactorForDisplay(int64_t display_id) {
+  // TODO(jonross): Remove this once aura-mus is complete. Currently the screen
+  // is not being set properly for mus-in-rendered. (http://crbug.com/659155)

[sky, 2016/11/29 20:27:47]

'rendered' -> 'renderer'

[jonross, 2016/11/29 20:57:57]

Done.

+  if (!display::Screen::GetScreen())
+    return 1.f;
+
   // TODO(riajiang): Change to use display::GetDisplayWithDisplayId() after
   // https://codereview.chromium.org/2361283002/ is landed.
   std::vector<display::Display> displays =
       display::Screen::GetScreen()->GetAllDisplays();
   auto iter = std::find_if(displays.begin(), displays.end(),
                            [display_id](const display::Display& display) {
                              return display.id() == display_id;
                            });
   if (iter != displays.end())
     return iter->device_scale_factor();
@@ skipping 1418 matching lines @@
     // TODO(riajiang): Figure out if |offset| needs to be converted.
     // (http://crbugs.com/646932)
     window_manager_internal_client_->SetUnderlaySurfaceOffsetAndExtendedHitArea(
         server_id(window), offset.x(), offset.y(),
         gfx::ConvertInsetsToDIP(ScaleFactorForDisplay(window->display_id()),
                                 hit_area));
   }
 }
 
 }  // namespace ui