Use platform's device scale factor for cursor

ash/display/display_manager.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 "ash/display/display_manager.h"
 
 #include <cmath>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 820 matching lines @@
 
 size_t DisplayManager::GetNumDisplays() const {
   return displays_.size();
 }
 
 bool DisplayManager::IsMirrored() const {
   return mirrored_display_id_ != gfx::Display::kInvalidDisplayID;
 }
 
 const DisplayInfo& DisplayManager::GetDisplayInfo(int64 display_id) const {
+  DCHECK_NE(gfx::Display::kInvalidDisplayID, display_id);
+
   std::map<int64, DisplayInfo>::const_iterator iter =
       display_info_.find(display_id);
   CHECK(iter != display_info_.end()) << display_id;
   return iter->second;
 }
 
 std::string DisplayManager::GetDisplayNameForId(int64 id) {
   if (id == gfx::Display::kInvalidDisplayID)
     return l10n_util::GetStringUTF8(IDS_ASH_STATUS_TRAY_UNKNOWN_DISPLAY_NAME);
 
@@ skipping 264 matching lines @@
       new_secondary_origin.Offset(-secondary_bounds.width(), offset);
       break;
   }
   gfx::Insets insets = secondary_display->GetWorkAreaInsets();
   secondary_display->set_bounds(
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 }  // namespace ash