Fix for issue 1728: raster vs. gpu text draws with the wrong color

The blend mode for LCD text was not set up correctly when using colors with alpha. This takes the color's alpha value
into account when setting up the blending function.

BUG=Skia:1728
R=bsalomon@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/45363002

git-svn-id: http://skia.googlecode.com/svn/trunk@11980 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed