Adding manual test to verify the absence of a race condition in GL texture filtering with canvas

This is a regression test. A race condition between the Chromium
compositor and skia's SkSurface_Gpu::onCopyOnWrite is causing the
texture filtering mode to be unstable in the compositor. This
produces a visible flickering effect when presinting zoomed canvases
with fine grained textured images.

BUG=415100

Review URL: https://codereview.chromium.org/595653002

git-svn-id: svn://svn.chromium.org/blink/trunk@182506 bbb929c8-8fbe-4397-9dbb-9b2b20218538