Fix ModeColorFilterEffect assert during GLProgramsTest

Select random filter mode for the test-case until the mode is not
Dst. SkModeColorFilter with Dst mode will not create a
ModeColorFilterEffect, and thus the case is not implemented.

Also changes it so that each call to ModeColorFilterEffect::TestCreate
creates a new GrEffect. Previously only one static effect was ever
created, due to copy-paste error.

R=bsalomon@google.com

Author: kkinnunen@nvidia.com

Review URL: https://codereview.chromium.org/39403002

git-svn-id: http://skia.googlecode.com/svn/trunk@11938 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed