Revert of Call EnsureWebKitInitialized() before registering extensions

Revert of Call EnsureWebKitInitialized() before registering extensions (patchset #3 id:40001 of https://codereview.chromium.org/1182083006/)

Reason for revert:
This seems the cause of many crashes

Original issue's description:
> Call EnsureWebKitInitialized() before registering extensions
>
> Blink needs to be initialized before registering an extension because:
> - WebScriptController::registerExtension() allocates an WTF::Vector on the first
>   call.
> - WTF::Vector uses PartitionAlloc.
> - PartitionAlloc's partitions needs to be initialized before allocating memory.
>   Blink initialization does the job.
>
> Before this CL, partitions are initialized lazily but lazy initialization
> doesn't provide proper histogram function, which might be the cause of missing
> report for PartitionAlloc.CommittedSize UMA.
>
> BUG=501171
>
> Committed: https://crrev.com/0d244fa5e106b3d146655a2c623539a3e1900831
> Cr-Commit-Position: refs/heads/master@{#339200}

TBR=jochen@chromium.org,haraken@chromium.org,kalman@chromium.org,kinuko@chromium.org,paulmeyer@chromium.org,sievers@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=501171
Committed: https://crrev.com/2b94b05fc252c9a006ae924d0fe75ed3abecbeb2
Cr-Commit-Position: refs/heads/master@{#339777}

[bashi, 2015-07-21 23:25:39]

Created Revert of Call EnsureWebKitInitialized() before registering extensions

[haraken, 2015-07-21 23:26:22]

LGTM

[commit-bot: I haz the power, 2015-07-21 23:26:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1244243003/1

[commit-bot: I haz the power, 2015-07-21 23:28:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-21 23:29:15]

Patchset 1 (id:??) landed as
https://crrev.com/2b94b05fc252c9a006ae924d0fe75ed3abecbeb2
Cr-Commit-Position: refs/heads/master@{#339777}

[bashi, 2015-07-28 00:42:05]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1258103005/ by bashi@chromium.org.

The reason for reverting is: It turns out this CL isn't the culprit of crashes.
Let's revert the revert..