Avoid overflow when checking if a transform is integer translation.

ui/gfx/transform.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_H_
 #define UI_GFX_TRANSFORM_H_
 
 #include <iosfwd>
 #include <string>
 
@@ skipping 122 matching lines @@
   bool IsApproximatelyIdentityOrTranslation(SkMScalar tolerance) const;
 
   // Returns true if the matrix is either a positive scale and/or a translation.
   bool IsPositiveScaleOrTranslation() const {
     if (!IsScaleOrTranslation())
       return false;
     return matrix_.get(0, 0) > 0.0 && matrix_.get(1, 1) > 0.0 &&
            matrix_.get(2, 2) > 0.0;
   }
 
-  // Returns true if the matrix is either identity or pure, non-fractional
-  // translation.
+  // Returns true if the matrix is identity or, if the matrix consists only
+  // of a translation whose components can be represented as integers. Returns
+  // false if the translation contains a fractional component or is too large to
+  // fit in an integer.
   bool IsIdentityOrIntegerTranslation() const;
 
   // Returns true if the matrix had only scaling components.
   bool IsScale2d() const { return matrix_.isScale(); }
 
   // Returns true if the matrix is has only scaling and translation components.
   bool IsScaleOrTranslation() const { return matrix_.isScaleTranslate(); }
 
   // Returns true if axis-aligned 2d rects will remain axis-aligned after being
   // transformed by this matrix.
@@ skipping 124 matching lines @@
 };
 
 // This is declared here for use in gtest-based unit tests but is defined in
 // the //ui/gfx:test_support target. Depend on that to use this in your unit
 // test. This should not be used in production code - call ToString() instead.
 void PrintTo(const Transform& transform, ::std::ostream* os);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_TRANSFORM_H_