GTK: More removal of raw GtkWidget->allocation access.

chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc

Index: chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc
diff --git a/chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc b/chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc
index 22734f8f4591c00ca696ad4c028cc9311e5c0752..9874dfd32dfe815182ca380ad654d80b3d4d06c2 100644
--- a/chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc
+++ b/chrome/browser/ui/gtk/notifications/balloon_view_gtk.cc
@@ -417,15 +417,17 @@ gboolean BalloonViewImpl::OnContentsExpose(GtkWidget* sender,
   gdk_cairo_rectangle(cr, &event->area);
   cairo_clip(cr);
 
+  GtkAllocation allocation;
+  gtk_widget_get_allocation(sender, &allocation);
+
   // According to a discussion on a mailing list I found, these degenerate
   // paths are the officially supported way to draw points in Cairo.
   cairo_set_source_rgb(cr, 0, 0, 0);
   cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND);
   cairo_set_line_width(cr, 1.0);
-  cairo_move_to(cr, 0.5, sender->allocation.height - 0.5);
+  cairo_move_to(cr, 0.5, allocation.height - 0.5);
   cairo_close_path(cr);
-  cairo_move_to(cr, sender->allocation.width - 0.5,
-                    sender->allocation.height - 0.5);
+  cairo_move_to(cr, allocation.width - 0.5, allocation.height - 0.5);
   cairo_close_path(cr);
   cairo_stroke(cr);
   cairo_destroy(cr);