Remove --enable-slimming-paint from layout test command line

Remove --enable-slimming-paint from layout test command line

Slimming paint has been enabled by default, so we don't need to force
it for layout tests.

Also Android no longer blocks slimming paint.

BUG=497950
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197940

[Xianzhu, 2015-06-26 19:50:00]

wangxianzhu@chromium.org changed reviewers:
+ chrishtr@chromium.org, pdr@chromium.org

[pdr., 2015-06-26 19:51:21]

On 2015/06/26 at 19:50:01, wangxianzhu wrote:
> 

LGTM

[Xianzhu, 2015-06-26 19:53:50]

The CQ bit was checked by wangxianzhu@chromium.org

[commit-bot: I haz the power, 2015-06-26 19:54:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1212693002/20001

[commit-bot: I haz the power, 2015-06-26 21:06:40]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197940

[chrishtr, 2015-06-26 23:31:01]

Is this really safe? This keeps us from being able to easily turn off SP if
needed.

[Xianzhu, 2015-06-27 00:24:25]

I created this CL because we couldn't easily turn off SP for layout tests with
"run-webkit-tests --additional-driver-flag=--disable-slimming-paint" as
--enable-slimming-paint in the python script has higher priority.

I think when we need to turn off SP, we can revert this CL first, or create
another CL to let --additional-driver-flag="--disable-slimming-paint" work.