Fix color pickers on WebView.

Fix color pickers on WebView.

Instead of getting the activity from the WindowAndroid to use as a
context, just get the context from the ContentViewCore. In WebView,
contexts must be wrapped to enable proper class lookup for custom view
classes defined in the WebView APK and using the Activity directly was
circumventing the wrapper, causing color pickers to crash.

BUG=490616
Committed: https://crrev.com/2046d4f5a4bde936c772262f73eb91d62f100b5b
Cr-Commit-Position: refs/heads/master@{#332418}

[Torne, 2015-06-02 14:52:52]

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

[Ted C, 2015-06-02 16:43:26]

lgtm

[Torne, 2015-06-02 16:43:50]

The CQ bit was checked by torne@chromium.org

[commit-bot: I haz the power, 2015-06-02 16:44:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1156883004/1

[commit-bot: I haz the power, 2015-06-02 17:22:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-02 17:23:34]

Patchset 1 (id:??) landed as
https://crrev.com/2046d4f5a4bde936c772262f73eb91d62f100b5b
Cr-Commit-Position: refs/heads/master@{#332418}