Animate the accessibility focus ring and fix some minor visual issues.

chrome/browser/chromeos/ui/accessibility_focus_ring_layer.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 "chrome/browser/chromeos/ui/accessibility_focus_ring_layer.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "ui/aura/window.h"
 #include "ui/compositor/layer.h"
 #include "ui/gfx/canvas.h"
 
 namespace chromeos {
 
 namespace {
 
 // The number of pixels in the color gradient that fades to transparent.
-const int kGradientWidth = 10;
+const int kGradientWidth = 6;
 
 // The color of the focus ring. In the future this might be a parameter.
 const int kFocusRingColorRed = 247;
 const int kFocusRingColorGreen = 152;
 const int kFocusRingColorBlue = 58;
 
 int sign(int x) {
   return ((x > 0) ? 1 : (x == 0) ? 0 : -1);
 }
 
@@ skipping 81 matching lines @@
 
 void AccessibilityFocusRingLayer::OnPaintLayer(gfx::Canvas* canvas) {
   gfx::Vector2d offset = layer()->bounds().OffsetFromOrigin();
 
   SkPaint paint;
   paint.setFlags(SkPaint::kAntiAlias_Flag);
   paint.setStyle(SkPaint::kStroke_Style);
   paint.setStrokeWidth(2);
 
   SkPath path;
-  for (int i = 0; i < kGradientWidth; i++) {
+  const int w = kGradientWidth;
+  for (int i = 0; i < w; ++i) {
     paint.setColor(
         SkColorSetARGBMacro(
-            255 - (255 * i / kGradientWidth),
+            255 * (w - i) * (w - i) / (w * w),
             kFocusRingColorRed, kFocusRingColorGreen, kFocusRingColorBlue));
     path = MakePath(ring_, i, offset);
     canvas->DrawPath(path, paint);
   }
 }
 
 }  // namespace chromeos