Fix SkBitmapOperations::CreateDropShadow drawing too large a shadow.

ui/gfx/skbitmap_operations.cc

Index: ui/gfx/skbitmap_operations.cc
diff --git a/ui/gfx/skbitmap_operations.cc b/ui/gfx/skbitmap_operations.cc
index 76aa763fa43905a6a20a1ecfe74276f4349ed929..55328ff1e01aa5a5afbe8aae300113948a3782f3 100644
--- a/ui/gfx/skbitmap_operations.cc
+++ b/ui/gfx/skbitmap_operations.cc
@@ -741,9 +741,11 @@ SkBitmap SkBitmapOperations::CreateDropShadow(
     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);