Several places were setting GL_UNPACK_ALIGNMENT
unneccessarily, whereas other places were assuming an
unpack alignment of 1. Since we never actually
do explicit row-alignment, set GL_UNPACK_ALIGNMENT
to 1 at context creation time and never change it
Bug: 26584230
Also turns on aggressive glGetError checking to
better catch potential problem zones
Change-Id: I190c8f0f0494a7f046d5ed769405c75d363be59a
bug:22390304
Fixes two issues:
1) The max texture unit wasn't large enough to handle the most complex
ComposeShader case (1 for draw primitive, 2 for gradient shader, 1 for
bitmap shader).
2) If a shader isn't supported by SkiaShader::store, the shader data
needs to be explicitly disabled, so we won't read uninitilized data
from it when trying to read shader information out.
Change-Id: I29ee7b7c1e07f67db88c1707bdc857daa305e713
