Revert of Enable HTMLMediaElement@autoplay on Android

Revert of Enable HTMLMediaElement@autoplay on Android (https://codereview.chromium.org/447353002/)

Reason for revert:
I misunderstood the outcome of the discussion surrounding this topic. We need to keep this code in order to not break google.com while gathering data about this feature.

Original issue's description:
> Enable HTMLMediaElement@autoplay on Android
> 
> This CL sets user_gesture_required_for_media_playback to false in Chrome for
> Android. Previously, we removed this requirement as a special case for the
> Google Search Results page. Now that this setting matches Chrome's behavior on
> other platforms, we don't need the special case for google.com and can remove
> the entire VoiceSearchTabHelper.
> 
> This CL leaves the user_gesture_required_for_media_playback WebPreference
> because that's used by android_webview.
> 
> R=klobag@chromium.org, darin@chromium.org
> BUG=178297
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=288308

TBR=darin@chromium.org,klobag@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=178297
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=288389

[abarth-chromium, 2014-08-08 17:48:12]

Created Revert of Enable HTMLMediaElement@autoplay on Android

[commit-bot: I haz the power, 2014-08-08 17:50:12]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/453023002/1

[commit-bot: I haz the power, 2014-08-08 17:52:15]

Change committed as 288389