Revert of Cache --whitelisted-extension-id in SimpleFeature.

Revert of Cache --whitelisted-extension-id in SimpleFeature. (patchset #13 id:240001 of https://codereview.chromium.org/1047943002/)

Reason for revert:
https://code.google.com/p/chromium/issues/detail?id=476061

Causing consistent errors on a variety of memory bots in both InitValueManifestTest.InitFromValueInvalid and LauncherPageManifestTest.ValidLauncherPage tests.

Original issue's description:
> Cache --whitelisted-extension-id in SimpleFeature.
>
> During startup, CommandLine::HasSwitch(kWhitelistedExtensionID) is
> called ~1000 times by SimpleFeature. It is the most common switch
> lookup, the second being kAppsGalleryUpdateUrl at ~300 times.
>
> Caching this avoids allocating and copying the string each time.
>
> BUG=471976
>
> Committed: https://crrev.com/16ca320592ce7ef6cd36500da6e670cc645781cd
> Cr-Commit-Position: refs/heads/master@{#324583}

TBR=tapted@chromium.org,kalman@chromium.org,mfoltz@chromium.org,jackhou@chromium.org
BUG=471976
Committed: https://crrev.com/473f21ef56a6fa05bfe0afc79fe5893d3ae804b4
Cr-Commit-Position: refs/heads/master@{#324695}

[Mike Lerman, 2015-04-10 19:58:25]

Created Revert of Cache --whitelisted-extension-id in SimpleFeature.

[commit-bot: I haz the power, 2015-04-10 20:43:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1076393002/1

[commit-bot: I haz the power, 2015-04-10 22:16:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-10 22:17:24]

Patchset 1 (id:??) landed as
https://crrev.com/473f21ef56a6fa05bfe0afc79fe5893d3ae804b4
Cr-Commit-Position: refs/heads/master@{#324695}