Align physical pixels of scrolled layers

cc/math_util.h

 // Copyright 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 CC_MATH_UTIL_H_
 #define CC_MATH_UTIL_H_
 
+#include <cmath>
+
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/cc_export.h"
 #include "ui/gfx/point_f.h"
 #include "ui/gfx/point3_f.h"
 #include "ui/gfx/size.h"
 #include "ui/gfx/transform.h"
 
 namespace base {
 class Value;
@@ skipping 56 matching lines @@
     static const double PI_DOUBLE;
     static const float PI_FLOAT;
     static const double EPSILON;
 
     static double Deg2Rad(double deg)  { return deg * PI_DOUBLE / 180; }
     static double Rad2Deg(double rad)  { return rad * 180 / PI_DOUBLE; }
 
     static float Deg2Rad(float deg)  { return deg * PI_FLOAT / 180; }
     static float Rad2Deg(float rad)  { return rad * 180 / PI_FLOAT; }
 
+    static float Round(float f)  { return (f > 0.f) ? std::floor(f + 0.5f) : std::ceil(f - 0.5f); }
+    static double Round(double d)  { return (d > 0.0) ? std::floor(d + 0.5) : std::ceil(d - 0.5); }
+
     // Background: Existing transform code does not do the right thing in
     // mapRect / mapQuad / projectQuad when there is a perspective projection that causes
     // one of the transformed vertices to go to w < 0. In those cases, it is necessary to
     // perform clipping in homogeneous coordinates, after applying the transform, before
     // dividing-by-w to convert to cartesian coordinates.
     //
     // These functions return the axis-aligned rect that encloses the correctly clipped,
     // transformed polygon.
     static gfx::Rect mapClippedRect(const gfx::Transform&, const gfx::Rect&);
     static gfx::RectF mapClippedRect(const gfx::Transform&, const gfx::RectF&);
@@ skipping 33 matching lines @@
     // Returns a base::Value representation of the floating point value.
     // If the value is inf, returns max double/float representation.
     static scoped_ptr<base::Value> asValueSafely(double value);
     static scoped_ptr<base::Value> asValueSafely(float value);
 
 };
 
 } // namespace cc
 
 #endif  // CC_MATH_UTIL_H_