Don't use drag to corner resizing for unresizable windows

ash/wm/window_util.h

Index: ash/wm/window_util.h
diff --git a/ash/wm/window_util.h b/ash/wm/window_util.h
index ec90805c020b65ee5fbf07bd8d1af33b95c2f290..83241e4ff1c8013cf79c5a872fbabf8b23635b36 100644
--- a/ash/wm/window_util.h
+++ b/ash/wm/window_util.h
@@ -48,6 +48,9 @@ ASH_EXPORT bool IsActiveWindowFullscreen();
 // Returns true if |window| can be maximized.
 ASH_EXPORT bool CanMaximizeWindow(const aura::Window* window);
 
+// Returns true if |window| can be resized.
+ASH_EXPORT bool CanResizeWindow(const aura::Window* window);
+
 // Returns true if |window| is normal or default.
 ASH_EXPORT bool IsWindowNormal(const aura::Window* window);