canvas2d: Add disable copy-on-write for Webview.

Add the copy-on-write disabled workaround for webview to the shared
image path.

R=kbr@chromium.org

Bug: 946792
Change-Id: I409b8666c5f59702f2d3e6c222d82f73b443271a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610872
Commit-Queue: Khushal <khushalsagar@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Auto-Submit: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660299}
2 files changed