Fix xfermode usage in GLES20Canvas.drawColor
Fix xfermode usage in GLES20Canvas.drawColor

bug:15762917

Was previously casting the SkPorterDuff::Mode directly into
SkXfermode::Mode, which is incorrect. Now convert as a first step, as
Canvas does.

Change-Id: I66695b08866ca2008b17f2ff30a36d9ed4d2ed80

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base