Fix SkBitmapOperations::CreateDropShadow drawing too large a shadow.

ui/gfx/skbitmap_operations.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 "ui/gfx/skbitmap_operations.h"
 
 #include <string.h>
 #include <algorithm>
 
 #include "base/logging.h"
@@ skipping 723 matching lines @@
   SkCanvas canvas(image_with_shadow);
   canvas.translate(SkIntToScalar(shadow_margin.left()),
                    SkIntToScalar(shadow_margin.top()));
 
   SkPaint paint;
   for (size_t i = 0; i < shadows.size(); ++i) {
     const gfx::ShadowValue& shadow = shadows[i];
     SkBitmap shadow_image = SkBitmapOperations::CreateColorMask(bitmap,
                                                                 shadow.color());
 
+    // The blur is halved to produce a shadow that correctly fits within the
+    // |shadow_margin|.
+    SkScalar sigma = SkDoubleToScalar(shadow.blur() / 2);
     skia::RefPtr<SkBlurImageFilter> filter =
-        skia::AdoptRef(SkBlurImageFilter::Create(
-            SkDoubleToScalar(shadow.blur()), SkDoubleToScalar(shadow.blur())));
+        skia::AdoptRef(SkBlurImageFilter::Create(sigma, sigma));
     paint.setImageFilter(filter.get());
 
     canvas.saveLayer(0, &paint);
     canvas.drawBitmap(shadow_image,
                       SkIntToScalar(shadow.x()),
                       SkIntToScalar(shadow.y()));
     canvas.restore();
   }
 
   canvas.drawBitmap(bitmap, SkIntToScalar(0), SkIntToScalar(0));
@@ skipping 27 matching lines @@
   canvas.translate(SkFloatToScalar(result.width() * 0.5f),
                    SkFloatToScalar(result.height() * 0.5f));
   canvas.rotate(angle);
   canvas.translate(-SkFloatToScalar(source.width() * 0.5f),
                    -SkFloatToScalar(source.height() * 0.5f));
   canvas.drawBitmap(source, 0, 0);
   canvas.flush();
 
   return result;
 }