Update from https://crrev.com/316786

ui/gfx/transform_util.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_GFX_TRANSFORM_UTIL_H_
 #define UI_GFX_TRANSFORM_UTIL_H_
 
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/transform.h"
 
@@ skipping 40 matching lines @@
 
 // Composes a transform from the given translation, scale, skew, prespective,
 // and rotation components following the routines detailed in this spec:
 // http://www.w3.org/TR/css3-3d-transforms/.
 GFX_EXPORT Transform ComposeTransform(const DecomposedTransform& decomp);
 
 GFX_EXPORT bool SnapTransform(Transform* out,
                               const Transform& transform,
                               const Rect& viewport);
 
+// Computes the Frobenius norm of (a - b).
+GFX_EXPORT float MatrixDistance(const Transform& a, const Transform& b);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_TRANSFORM_UTIL_H_