Add a confirmation prompt to app uninstallation on the ntp.

Add a confirmation prompt to app uninstallation on the ntp.

The uninstall dialog used to say:

[===============================x]
|Confirm Uninstallation          |
|--------------------------------|
|<b>Uninstall Foo Extension?</b> |
|                                |
|Are you sure you want to        |
|uninstall this extension?       |
|                                |
|================================|

We don't have the bottom string with the word 'app', and I
realized it is somewhat extraneous anyway. So just removed it
in all cases and de-bolded the text above. Looks much better.

Also, fixed a bug where the icon we display in the GTK
dialogs is too big by doing image resizing in
ExtensionInstallUI.

BUG=54874
TEST=Uninstall app and extension. Both should have a prompt,
and UI layout should be the same.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=59157

[Matt Perry, 2010-09-09 18:24:51]

LGTM

[Aaron Boodman, 2010-09-10 20:20:56]

I had to do some touch-up on Windows to make the text label in the dialog layout
vertically centered wrt the icon.

I also removed all the shortcut creation logic from that dialog since we don't
use it anymore.

[Matt Perry, 2010-09-10 20:37:47]

LGTM2