Fix background blending for some cases where it did not work at all. The fix adds the blendMode parameter to the Image subclass drawing function call, instead of using the default normal blend mode. In some cases this involved adding a new BlendMode parameter to the draw* function. The fixed cases were:
 - background data URI SVG images, when a border-style was added to the container
 - tiled (repeated) gradient backgrounds
 - cross-fade image backgrounds

R=eseidel@chromium.org
BUG=268821

Review URL: https://chromiumcodereview.appspot.com/22596003

git-svn-id: svn://svn.chromium.org/blink/trunk@155773 bbb929c8-8fbe-4397-9dbb-9b2b20218538
12 files changed