Add common GLFence::IsSupported() check

Add common GLFence::IsSupported() check

Cconsolidate the logic inside gl_fence.cc
to allow checking if a GLFence can be created.

R=reveman@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278860

[no sievers, 2014-06-16 22:43:54]

ptal.

Recent fence blacklisting broke the incomplete checks in mailbox_synchronizer.cc
and texture_definition.cc (they were only looking for EGL_KHR_fence_sync
although es3 supports fences too).

This patch still needs https://codereview.chromium.org/332303002/ to land first
which allows me to override how we initialize the extension booleans.

https://codereview.chromium.org/331293003/diff/1/gpu/command_buffer/service/f...
File gpu/command_buffer/service/feature_info_unittest.cc (left):

https://codereview.chromium.org/331293003/diff/1/gpu/command_buffer/service/f...
gpu/command_buffer/service/feature_info_unittest.cc:1019:
EXPECT_TRUE(info_->feature_flags().use_async_readpixels);
This test is bad. EGL_KHR_fence_sync is not a GL extension, so it's not a valid
test to add it to the GL_EXTENSIONS string here used to init FeatureInfo.

There are currently no mock EGL bindings, that's why I added no tests here for
EGL_KHR_fence_sync

[reveman, 2014-06-17 00:50:05]

lgtm

https://codereview.chromium.org/331293003/diff/1/ui/gl/gl_fence.cc
File ui/gl/gl_fence.cc (right):

https://codereview.chromium.org/331293003/diff/1/ui/gl/gl_fence.cc#newcode180
ui/gl/gl_fence.cc:180: DCHECK(!!fence.get() == GLFence::IsSupported());
DCHECK_EQ?

[no sievers, 2014-06-20 20:17:34]

The CQ bit was checked by sievers@chromium.org

[commit-bot: I haz the power, 2014-06-20 20:20:59]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sievers@chromium.org/331293003/80001

[no sievers, 2014-06-20 23:33:22]

Committed patchset #6 manually as r278860 (presubmit successful).