Don't scale mask image for new tab button.

chrome/browser/ui/views/tabs/tab_strip.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 "chrome/browser/ui/views/tabs/tab_strip.h"
 
 #if defined(OS_WIN)
 #include <windowsx.h>
 #endif
 
@@ skipping 408 matching lines @@
       break;
     default:
       NOTREACHED();
       break;
   }
 
   gfx::ImageSkia* mask =
       GetThemeProvider()->GetImageSkiaNamed(IDR_NEWTAB_BUTTON_MASK);
   int height = mask->height();
   int width = mask->width();
+
+  // The canvas and mask has to use the same scale factor.
+  if (!mask->HasRepresentation(scale_factor))
+    scale_factor = ui::SCALE_FACTOR_100P;
+
   gfx::Canvas canvas(gfx::Size(width, height), scale_factor, false);
 
   // For custom images the background starts at the top of the tab strip.
   // Otherwise the background starts at the top of the frame.
   gfx::ImageSkia* background =
       GetThemeProvider()->GetImageSkiaNamed(background_id);
   int offset_y = GetThemeProvider()->HasCustomImage(background_id) ?
       0 : background_offset_.y();
 
   // The new tab background is mirrored in RTL mode, but the theme background
@@ skipping 2131 matching lines @@
   if (!adjust_layout_)
     return false;
 
 #if !defined(OS_CHROMEOS)
   if (ui::GetDisplayLayout() != ui::LAYOUT_TOUCH)
     return false;
 #endif
 
   return true;
 }