Remove android_webview_build conditions from base.

Remove android_webview_build conditions from base.

Remove references to android_webview_build now that we no longer support
that build configuration. Fold all conditions into the general
OS==android sections.

BUG=440793
Committed: https://crrev.com/7aba6ac8106b2ff684fe06fc7197393dcd7a6965
Cr-Commit-Position: refs/heads/master@{#322087}

[Torne, 2015-03-24 20:51:38]

torne@chromium.org changed reviewers:
+ thakis@chromium.org

[Nico, 2015-03-24 21:10:33]

lgtm

[Nico, 2015-03-24 21:47:57]

The CQ bit was checked by thakis@chromium.org

[commit-bot: I haz the power, 2015-03-24 21:48:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1010653003/1

[commit-bot: I haz the power, 2015-03-24 23:04:42]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-24 23:05:25]

Patchset 1 (id:??) landed as
https://crrev.com/7aba6ac8106b2ff684fe06fc7197393dcd7a6965
Cr-Commit-Position: refs/heads/master@{#322087}