Revert of Remove smiluate-touch-screen-with-mouse content flag.

Revert of Remove smiluate-touch-screen-with-mouse content flag. (https://codereview.chromium.org/258503003/)

Reason for revert:
Somewhat speculative; looks like this caused TouchEmulatorTest failures on valgrind:

http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28tsan%29%283%29/builds/11052

TouchEmulatorTest.Pinch:
../../content/browser/renderer_host/input/touch_emulator_unittest.cc:254: Failure
Value of: ExpectedEvents()
Actual: "TouchEnd GestureFlingStart"
Expected: "TouchEnd GestureScrollEnd"

etc

Original issue's description:
> Remove smiluate-touch-screen-with-mouse content flag.
> 
> This is duplicated functionality now, as one can use DevTools touch emulation instead.
> 
> BUG=337142
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266549

TBR=aelias@chromium.org,jochen@chromium.org,dgozman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=337142
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266608

[Nico, 2014-04-28 18:13:09]

Created Revert of Remove smiluate-touch-screen-with-mouse content flag.

[commit-bot: I haz the power, 2014-04-28 18:14:40]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/260123003/1

[commit-bot: I haz the power, 2014-04-28 18:15:44]

Change committed as 266608

[jdduke (slow), 2014-04-28 18:20:31]

On 2014/04/28 18:15:44, I haz the power (commit-bot) wrote:
> Change committed as 266608

Hmm, those failures are most likely from
https://codereview.chromium.org/250923005/ (r266548).

[Nico, 2014-04-28 18:26:20]

On 2014/04/28 18:20:31, jdduke wrote:
> On 2014/04/28 18:15:44, I haz the power (commit-bot) wrote:
> > Change committed as 266608
> 
> Hmm, those failures are most likely from
> https://codereview.chromium.org/250923005/ (r266548).

Sorry, copy-paste error, I meant to revert that one :-(

[Nico, 2014-04-28 18:27:04]

A revert of this CL has been created in
https://codereview.chromium.org/256203003/ by thakis@chromium.org.

The reason for reverting is: I meant to revert
https://codereview.chromium.org/250923005/ , not this one..