Allow user script install by dragging onto chrome://extensions/.

Allow user script install by dragging onto chrome://extensions/.

Because otherwise, when off-store extension install is disabled,
there is no way to install user scripts.

BUG=55584
TEST=Run chrome with --enable-off-store-extension-install=0, navigate to a .user.js file. Should see error. Now download that file and drag onto chrome://extensions/. Should be offered a drop target, and install should proceed when dropped.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=139640

[Yoyo Zhou, 2012-05-29 19:08:11]

http://codereview.chromium.org/10449008/diff/1003/chrome/browser/ui/webui/ext...
File chrome/browser/ui/webui/extensions/install_extension_handler.cc (right):

http://codereview.chromium.org/10449008/diff/1003/chrome/browser/ui/webui/ext...
chrome/browser/ui/webui/extensions/install_extension_handler.cc:103:
CHECK(false);
Did you mean to put this in a different else?

[Aaron Boodman, 2012-05-30 00:42:50]

http://codereview.chromium.org/10449008/diff/1003/chrome/browser/ui/webui/ext...
File chrome/browser/ui/webui/extensions/install_extension_handler.cc (right):

http://codereview.chromium.org/10449008/diff/1003/chrome/browser/ui/webui/ext...
chrome/browser/ui/webui/extensions/install_extension_handler.cc:103:
CHECK(false);
On 2012/05/29 19:08:12, Yoyo Zhou wrote:
> Did you mean to put this in a different else?

opps

[Yoyo Zhou, 2012-05-30 00:46:32]

LGTM