Fix error logging in ValidateBlitFramebufferANGLE
Fix error logging in ValidateBlitFramebufferANGLE

Bundle an error message about whole buffer copies inside gl::Error
instead of delivering it to the Platform.

BUG=angleproject:1660

Change-Id: I13205b74529fbe40af05e7c1896c6315486e90e0
Reviewed-on: https://chromium-review.googlesource.com/437628
Commit-Queue: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

MSOpenTech/angle,ppy/angle,ecoal95/angle,MSOpenTech/angle,ecoal95/angle,MSOpenTech/angle,ppy/angle,ecoal95/angle,ecoal95/angle,ppy/angle,ppy/angle,MSOpenTech/angle,ecoal95/angle