gpu: workaround force_cube_map_positive_x_allocation fixes Android crash.
Adreno Android (e.g. Nexus5) crashes on allocating a cube map texture bound to FBO, if
the CUBE_MAP_POSITIVE_X texture is not allocated yet. The Workaround forces to allocate
the CUBE_MAP_POSITIVE_X texture.
Add new unittests to prevent regression. ANGLE crashes on GLCubeMapTextureTest.ReadPixels
It's will be fixed in ANGLE project.
TEST=gl_tests.GLCubeMapTextureTests.*
BUG=518889
Review URL: https://codereview.chromium.org/1280163004
Cr-Commit-Position: refs/heads/master@{#343600}
8 files changed
