Add --disable-accelerated-2d-canvas
Add --disable-accelerated-2d-canvas

The accelerated 2D canvas is causing issues with web applications
using <canvas> heavily.

BUG=chromium:142913
TEST=none

Change-Id: I1b52caf53868f29fa53472919c6d7077d26bba8e
Reviewed-on: https://gerrit.chromium.org/gerrit/30435
Reviewed-by: Chris Masone <98e3d65c6b0e9e2391eb4c2e8b1e572b77e544ed@chromium.org>
Reviewed-by: Zelidrag Hornung <2423ba2b026624ad482ad8e6887b2d657f9c0c43@chromium.org>
Tested-by: Satoru Takabayashi <59864788db41f0f5af51640995670e228eeb7e4d@chromium.org>
Commit-Ready: Satoru Takabayashi <59864788db41f0f5af51640995670e228eeb7e4d@chromium.org>

chadversary/chromiumos.platform.login_manager,chadversary/chromiumos.platform.login_manager,chadversary/chromiumos.platform.login_manager