Fix stroke color definition of canvas context.

Fix stroke color definition of canvas context.

The stroke's color of a canvas can be given with the combination
of a CSS color and an optional alpha value. The color part can be
defined with both basic or extended color keywords. Using a basic keyword
with an alpha value works fine but it does not work with extended colors.
The reason is that blink::CanvasStyle::createFromStringWithOverrideAlpha
is not prepared for getting a system color. This is basically due to
a missing case branch. The patch supplies this missing branch.

R=rob.buis@samsung.org,schenney@chromium.org
BUG=434812
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185656

[Stephen Chennney, 2014-11-19 20:11:12]

schenney@chromium.org changed reviewers:
+ junov@chromium.org, senorblanco@chromium.org

[Stephen Chennney, 2014-11-19 20:11:12]

+junov, +senorblanco

[Justin Novosad, 2014-11-19 20:21:22]

On 2014/11/19 20:11:12, Stephen Chenney wrote:
> +junov, +senorblanco

lgtm

[Stephen White, 2014-11-19 21:10:09]

LGTM w/nits

https://codereview.chromium.org/725913003/diff/1/LayoutTests/canvas/stroke-wi...
File LayoutTests/canvas/stroke-with-system-color-and-alpha-crash.html (right):

https://codereview.chromium.org/725913003/diff/1/LayoutTests/canvas/stroke-wi...
LayoutTests/canvas/stroke-with-system-color-and-alpha-crash.html:3: <p>PASS if
Blink does not crashes in debug.</p>
Nits: Blink -> it, crashes -> crash

[reni, 2014-11-20 09:36:55]

The CQ bit was checked by rhodovan.u-szeged@partner.samsung.com

[commit-bot: I haz the power, 2014-11-20 09:37:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/725913003/20001

[commit-bot: I haz the power, 2014-11-20 10:21:42]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=185656

[reni, 2014-11-20 10:38:15]

Thanks for the reviews!