Antialias the dragged-link rounded rect

Please see bug 661412 comments #0 and chromium#1 for a before/after to explain what this CL does.

R=eae@chromium.org
BUG=661412

Review-Url: https://codereview.chromium.org/2471533004
Cr-Commit-Position: refs/heads/master@{#429360}

third_party/WebKit/Source/platform/DragImage.cpp

@@ -257,6 +257,7 @@ std::unique_ptr<DragImage> DragImage::create(const KURL& url,
   IntRect rect(IntPoint(), imageSize);
   SkPaint backgroundPaint;
   backgroundPaint.setColor(SkColorSetRGB(140, 140, 140));
+  backgroundPaint.setAntiAlias(true);
   SkRRect rrect;
   rrect.setRectXY(SkRect::MakeWH(imageSize.width(), imageSize.height()),
                   DragLabelRadius, DragLabelRadius);