Skia: bug fix for SkBitmapProcState_shaderproc.h

Take care of "dx" being 0 case

Change-Id: Ie492c0454d6c8876ea9bb48e911de77cc78a8e98
Merge branch 'cm' into HEAD
Android.mk #LOCAL_CFLAGS += -fno-strict-aliasing

Change-Id: I523a8e2fd214e6f4044b86b2383ab44752fd9c1c