It turns out I had the sense of the GetLocalBounds bool wrong everywhere, so ...

views/window/dialog_client_view.cc

Index: views/window/dialog_client_view.cc
===================================================================
--- views/window/dialog_client_view.cc	(revision 74228)
+++ views/window/dialog_client_view.cc	(working copy)
@@ -434,7 +434,7 @@
     //             a theme-supplied gripper. We should probably improvise
     //             something, which would also require changing |gripper_size|
     //             to have different default values, too...
-    size_box_bounds_ = GetLocalBounds();
+    size_box_bounds_ = GetContentsBounds();
     size_box_bounds_.set_x(size_box_bounds_.right() - gripper_size.cx);
     size_box_bounds_.set_y(size_box_bounds_.bottom() - gripper_size.cy);
     RECT native_bounds = size_box_bounds_.ToRECT();