16-bit video upload to float: intermediate R16_EXT and copy to float.
R16_EXT is supported on desktop core profile (OSX and Linux), and via
OpenGL ES 3.1 GL_EXT_texture_norm16 extension (including ANGLE on Windows).
Update khronos headers to get GL_R16_EXT definition.
It is not exposed through WebGL but only used internally.
Brings significant performance improvement, cutting the time spent on
WebGL TexImage2D from ~1.2ms to ~0.2ms - see https://crbug.com/624436.
BUG=624436
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Review-Url: https://codereview.chromium.org/2767063002
Cr-Commit-Position: refs/heads/master@{#467924}
34 files changed