Revert 282393 "Do not call glDrawBuffersARB when the extension i..."

Revert 282393 "Do not call glDrawBuffersARB when the extension i..."

Broke gpu_unittests FramebufferInfoTest.DrawBuffers:
[ RUN      ] FramebufferInfoTest.DrawBuffers
../../gpu/command_buffer/service/framebuffer_manager_unittest.cc:653: Failure
Actual function call count doesn't match EXPECT_CALL(*gl_, DrawBuffersARB(kMaxDrawBuffers, _))...
         Expected: to be called once
           Actual: never called - unsatisfied and active
../../gpu/command_buffer/service/framebuffer_manager_unittest.cc:657: Failure
Actual function call count doesn't match EXPECT_CALL(*gl_, DrawBuffersARB(kMaxDrawBuffers, _))...
         Expected: to be called once
           Actual: never called - unsatisfied and active
[  FAILED  ] FramebufferInfoTest.DrawBuffers (1 ms)

> Do not call glDrawBuffersARB when the extension is absent
> 
> The function Framebuffer::ChangeDrawBuffersHelper was assuming
> that binding of an FBO with no GL_COLOR_ATTACHMENT0 was
> accompanied by setting the first draw buffer to GL_NONE with
> glDrawBuffersARB in the fix introduced in:
> https://codereview.chromium.org/315283002
> 
> When the extension is not present, it can be assumed that the
> glDrawBuffersARB state need not be set and restored.
> 
> BUG=(wrangling)
> NOTRY=True
> 
> Review URL: https://codereview.chromium.org/375413003

TBR=ccameron@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282402

[scherkus (not reviewing), 2014-07-10 19:50:53]

Committed patchset #1 manually as r282402 (tree was closed).