gpu: Implement GL_INTEL_framebuffer_CMAA via shaders in the GPU Service

Based on OpenGLES code developed by Filip Strugar and Jon Kennedy.

BUG=535198
TEST=Run a WebGL app with Chrome started with "--enable-cmaa-shaders"

Co-Authored-By: Filip Strugar <filip.strugar@intel.com>
Co-Authored-By: Jon Kennedy <jon.kennedy@intel.com>
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel;tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2055713003
Cr-Commit-Position: refs/heads/master@{#400438}
9 files changed