Unmirrors new tab button theme background in Rtl mode

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 402 matching lines @@
   int height = mask->height();
   int width = mask->width();
   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();
-  canvas.TileImageInt(*background, GetMirroredX() + background_offset_.x(),
-                      newtab_button_v_offset() + offset_y, 0, 0, width, height);
+
+  // The new tab background is mirrored in RTL mode, but the theme background
+  // should never be mirrored. Mirror it here to compensate.
+  float x_scale = 1.0f;
+  int x = GetMirroredX() + background_offset_.x();
+  if (base::i18n::IsRTL()) {
+    x_scale = -1.0f;
+    // Offset by |width| such that the same region is painted as if there was no
+    // flip.
+    x += width;
+  }
+  canvas.TileImageInt(*background, x, newtab_button_v_offset() + offset_y,
+                      x_scale, 1.0f, 0, 0, width, height);
 
   if (alpha != 255) {
     SkPaint paint;
     paint.setColor(SkColorSetARGB(alpha, 255, 255, 255));
     paint.setXfermodeMode(SkXfermode::kDstIn_Mode);
     paint.setStyle(SkPaint::kFill_Style);
     canvas.DrawRect(gfx::Rect(0, 0, width, height), paint);
   }
 
   // White highlight on hover.
@@ skipping 1906 matching lines @@
 
   int mini_tab_count = GetMiniTabCount();
   int normal_count = tab_count() - mini_tab_count;
   if (normal_count == 0 || normal_count == mini_tab_count)
     return false;
   int x = GetStartXForNormalTabs();
   int available_width = width() - x - new_tab_button_width();
   return (Tab::GetTouchWidth() * normal_count +
           tab_h_offset() * (normal_count - 1)) > available_width;
 }