mash: Partially migrate WorkspaceController to ash common.

ash/common/wm/wm_window_animations.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/common/wm/wm_window_animations.h"
+
+#include "ui/compositor/layer.h"
+#include "ui/gfx/transform.h"
+
+namespace ash {
+
+void SetTransformForScaleAnimation(ui::Layer* layer,
+                                   LayerScaleAnimationDirection type) {
+  // Scales for windows above and below the current workspace.
+  const float kLayerScaleAboveSize = 1.1f;
+  const float kLayerScaleBelowSize = .9f;
+
+  const float scale = type == LAYER_SCALE_ANIMATION_ABOVE
+                          ? kLayerScaleAboveSize
+                          : kLayerScaleBelowSize;
+  gfx::Transform transform;
+  transform.Translate(-layer->bounds().width() * (scale - 1.0f) / 2,
+                      -layer->bounds().height() * (scale - 1.0f) / 2);
+  transform.Scale(scale, scale);
+  layer->SetTransform(transform);
+}
+
+}  // namespace ash