GitLab

GLRenderer expects a BeginDrawingFrame before each
FinishDrawingFrame call.

This also makes sure GLRenderer::BeginDrawingFrame doesn't
early out before creating the read lock fence.

BUG=428071
R=danakj
TEST=cc_unittests --gtest_filter=GLRendererWithOverlaysTest.ResourcesExportedAndReturned

Review URL: https://codereview.chromium.org/669233003

Cr-Commit-Position: refs/heads/master@{#302730}