Fixing Canvas2DLayerBridge to handle lost graphics contexts

This patch detects lost contexts and attempts to restore canvas layers
to a usable state, whenever possible. If the layer can not be recovered
All operation that draw to and read from the canvas are skipped.

BUG=240881,226928,237799
R=senorblanco@chromium.org

Review URL: https://codereview.chromium.org/16032003

git-svn-id: svn://svn.chromium.org/blink/trunk@154134 bbb929c8-8fbe-4397-9dbb-9b2b20218538