commit fd383c4428d3a4e1041425214f001661dca8d173
author qiankun.miao <qiankun.miao@intel.com> Fri Jul 15 03:26:30 2016
committer Commit bot <commit-bot@chromium.org> Fri Jul 15 03:28:31 2016
tree 144c467a0aade0d8a968d492b1e271ef74b70a96
parent 84f273e96f9e3c7211a76f7866f816846790f3b7

Discard correct drawing buffer

This partly revert https://codereview.chromium.org/1950053003. On
platform supported GL_EXT_discard_framebuffer extension, it causes a
WebGL conformance test regression:
conformance/state/state-uneffected-after-compositing.html

The root cause is current bound fbo will be discarded other than the
default fbo. We should discard default fbo correctly.

BUG=628472

Review-Url: https://codereview.chromium.org/2145093003
Cr-Commit-Position: refs/heads/master@{#405689}