Fix tab strip rendering at non-integral scale factors in MD.

chrome/browser/ui/views/tabs/tab.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.h"
 
 #include <stddef.h>
 #include <limits>
 #include <utility>
 
@@ skipping 1638 matching lines @@
 
   // Extends the area to the bottom when the crash animation is in progress.
   if (crash_icon_animation_->is_animating())
     bounds.set_height(height() - bounds.y());
   bounds.set_x(GetMirroredXForRect(bounds));
   SchedulePaintInRect(bounds);
 }
 
 void Tab::GetFillPath(float scale, SkPath* fill) const {
   const float right = width() * scale;
-  const float bottom = height() * scale;
+  // The bottom of the tab needs to be pixel-aligned or else when we call
+  // ClipPath with anti-aliasing enabled it can cause artifacts.
+  const float bottom = std::ceil(height() * scale);
   const float unscaled_endcap_width = GetUnscaledEndcapWidth();
 
   fill->moveTo(right - 1, bottom);
   fill->rCubicTo(-0.75 * scale, 0, -1.625 * scale, -0.5 * scale, -2 * scale,
                  -1.5 * scale);
   fill->lineTo(right - 1 - (unscaled_endcap_width - 2) * scale, 2.5 * scale);
   // Prevent overdraw in the center near minimum width (only happens if
   // scale < 2).  We could instead avoid this by increasing the tab inset
   // values, but that would shift all the content inward as well, unless we
   // then overlapped the content on the endcaps, by which point we'd have a
@@ skipping 90 matching lines @@
   inactive_images_.image_c = rb.GetImageSkiaNamed(IDR_TAB_INACTIVE_CENTER);
   inactive_images_.image_r = rb.GetImageSkiaNamed(IDR_TAB_INACTIVE_RIGHT);
   inactive_images_.l_width = inactive_images_.image_l->width();
   inactive_images_.r_width = inactive_images_.image_r->width();
 
   mask_images_.image_l = rb.GetImageSkiaNamed(IDR_TAB_ALPHA_LEFT);
   mask_images_.image_r = rb.GetImageSkiaNamed(IDR_TAB_ALPHA_RIGHT);
   mask_images_.l_width = mask_images_.image_l->width();
   mask_images_.r_width = mask_images_.image_r->width();
 }