BrowserFontResource should not push opacity info to Blink
Blink's opacity & LCD logic is being removed - instead this is to be
handled by setting appropriate SkSurfaceProps onto the target canvas.
Unfortunately that's not directly applicable to
BrowserFontResource_Trusted::DrawTextAt/DrawTextToCanvas because the
API allows different opacity flags to be specified for different
calls directed to the same canvas.
We work around by disabling LCD text at the last stage, using a
temporary SkCanvas.
BUG=430617
R=reed@google.com,piman@chromium.org
Review URL: https://codereview.chromium.org/
975533004
Cr-Commit-Position: refs/heads/master@{#319645}