Revert of Move core web_view code to extensions.

Revert of Move core web_view code to extensions. (patchset #6 of https://codereview.chromium.org/496873006/)

Reason for revert:
This breaks the app_shell build for the reasons jamesr describes (src/extensions now depends on generated headers from src/chrome, but there cannot be a dependency from extensions -> chrome).

Hypothetical repro on Linux:
* rm -rf out/* && gclient runhooks && ninja -C out/Debug -j 1000 app_shell

chrome/browser/extensions/api/capture_web_contents_function.h:9:10: fatal error: 'chrome/common/extensions/api/types.h' file not found


Original issue's description:
> Move core web_view code to extensions.
> 
> 
> BUG=352290
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/1218a23163baab9f53d70e9a63030db13ef04d04

TBR=fsamuel@chromium.org,yoz@chromium.org,kalman@chromium.org,sky@chromium.org,dmazzoni@chromium.org,jamesr@chromium.org,hanxi@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=352290

[James Cook, 2014-08-25 23:31:12]

Created Revert of Move core web_view code to extensions.

[commit-bot: I haz the power, 2014-08-25 23:33:03]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/505893002/1

[Yoyo Zhou, 2014-08-25 23:56:37]

LGTM

[commit-bot: I haz the power, 2014-08-26 00:08:36]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-26 00:08:38]

Failed to commit the patch.