Lazily initialize the v8::Isolate used by ProxyResolverV8 (in the browser process).

Lazily initialize the v8::Isolate used by ProxyResolverV8 (in the browser process).

Also removes the limitation of ProxyResolverV8 not being available in single-process mode which no longer applies.

BUG=454983
Committed: https://crrev.com/929aa683d7deed9cf519dce2fa0da2c7bfda5c12
Cr-Commit-Position: refs/heads/master@{#318277}

[eroman, 2015-02-26 06:55:09]

eroman@chromium.org changed reviewers:
+ jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-02-26 15:06:31]

lgtm

[eroman, 2015-02-26 18:35:50]

The CQ bit was checked by eroman@chromium.org

[commit-bot: I haz the power, 2015-02-26 18:36:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/957933002/20001

[commit-bot: I haz the power, 2015-02-26 19:21:27]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-26 19:22:23]

Patchset 2 (id:??) landed as
https://crrev.com/929aa683d7deed9cf519dce2fa0da2c7bfda5c12
Cr-Commit-Position: refs/heads/master@{#318277}