Make GTK file dialog box modal for parent window, instead of for the entire...

Make GTK file dialog box modal for parent window, instead of for the entire
application.

This works by adding the top-level GtkWindow objects, such as BrowserWindowGtk
and BookmarkManagerGtk, to their own unique window groups. Without this change,
all top-level windows are added to a default application-wide window group.

This ensures that all grabs created with gtk_grab_add(...) only affect the
window group of the grabbed widget, as opposed to the entire application.

Note that gtk_window_set_modal(...) is implemented with gtk_grab_add(...) and
therefore is only modal to a specific window group.

In order for this to work correctly, changes were also made to the info
bubble and render widget popup (<select> tag) code. Since these widgets
also call gtk_grab_add(...), they must be added to the top level window
group to work correctly.

Test 1:
- Open two new chrome window: A and B
- Open "Save file as..." dialog in window A
- Verify that window A does not respond to keyboard or mouse events.
- Verify that window B does responde to keyboard and mouse events.
- Open "Save file as..." dialog in window B
- Verify that window B does not respond to keyboard or mouse events.
- Cancel dialog on window A.
- Verify that window A starts responding to keyboard and mouse events.
- Cancel dialog on window B.
- Verify that window B starts responding to keyboard and mouse events.

Test 2:
- Verify that <select> tag allows for correct selection of items.

Test 3:
- Click bookmark star and verify that info bubble works correctly.

BUG=8727
TEST=none

patch by Mohit Muthanna Cheppudira <mohit.muthanna [at] gmail>
original review url: <http://codereview.chromium.org/155852>;


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=21207