Implement WebGL2's uniform*() with sub source.

Implement WebGL2's uniform*() with sub source.

BUG=688598
TEST=conformance2/uniforms/*
R=kbr@chromium.org,kainino@chromium.org
CQ_INCLUDE_TRYBOTS=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/2692853006
Cr-Commit-Position: refs/heads/master@{#450544}
(cherry picked from commit bd3c00a7c7b91c60409cf5d4032c8269c7320c41)

Review-Url: https://codereview.chromium.org/2698863002 .
Cr-Commit-Position: refs/branch-heads/2987@{#538}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/3a7c59afb439110a3f91f9ad8be724b6e81f9bce

[Zhenyao Mo, 2017-02-16 01:40:12]

Description was changed from

==========
Implement WebGL2's uniform*() with sub source.

BUG=688598
TEST=conformance2/uniforms/*
R=kbr@chromium.org,kainino@chromium.org
CQ_INCLUDE_TRYBOTS=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/2692853006
Cr-Commit-Position: refs/heads/master@{#450544}
(cherry picked from commit bd3c00a7c7b91c60409cf5d4032c8269c7320c41)
==========

to

==========
Implement WebGL2's uniform*() with sub source.

BUG=688598
TEST=conformance2/uniforms/*
R=kbr@chromium.org,kainino@chromium.org
CQ_INCLUDE_TRYBOTS=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/2692853006
Cr-Commit-Position: refs/heads/master@{#450544}
(cherry picked from commit bd3c00a7c7b91c60409cf5d4032c8269c7320c41)

Review-Url: https://codereview.chromium.org/2698863002 .
Cr-Commit-Position: refs/branch-heads/2987@{#538}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/3a7c59afb439110a3f91f9ad8be7...
==========

[Zhenyao Mo, 2017-02-16 01:40:15]

Committed patchset #1 (id:1) manually as
3a7c59afb439110a3f91f9ad8be724b6e81f9bce.