Make gfx::Rect class operations consistently mutate the class they are called on.

ash/wm/window_util.cc

Index: ash/wm/window_util.cc
diff --git a/ash/wm/window_util.cc b/ash/wm/window_util.cc
index 8b9dcb0202f1384848da9e17043f7c0b13a21490..55513af6c4e147f7c0e4c0f76a1a18c9ad05efca 100644
--- a/ash/wm/window_util.cc
+++ b/ash/wm/window_util.cc
@@ -110,7 +110,8 @@ void ToggleMaximizedWindow(aura::Window* window) {
 void CenterWindow(aura::Window* window) {
   const gfx::Display display =
       Shell::GetScreen()->GetDisplayNearestWindow(window);
-  gfx::Rect center = display.work_area().Center(window->bounds().size());
+  gfx::Rect center = display.work_area();
+  center.ClampToCenteredSize(window->bounds().size());
   window->SetBounds(center);
 }