cc: Do not create separate tilings for almost equal scale factors.

cc/base/math_util.cc

 // 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.
 
 #include "cc/base/math_util.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
@@ skipping 102 matching lines @@
   (*num_vertices_in_clipped_quad)++;
 }
 
 static inline void AddVertexToClippedQuad3d(const gfx::Point3F& new_vertex,
                                             gfx::Point3F clipped_quad[8],
                                             int* num_vertices_in_clipped_quad) {
   clipped_quad[*num_vertices_in_clipped_quad] = new_vertex;
   (*num_vertices_in_clipped_quad)++;
 }
 
+float MathUtil::RoundToFixedPrecision(float value, int precision) {
+  // Return the same value, as higher precision is not possible with float.
+  if (precision < 1 || precision > (std::numeric_limits<float>::digits10 - 1))

[ericrk, 2015/10/19 16:40:50]

drive-by-nit: Should we DCHECK that precision >= 1? Or clamp to 1? returning the
full-precision number when a caller asks for precision 0 seems weird?

[vmpstr, 2015/10/19 18:58:38]

I agree, this should be a DCHECK instead of an early out.

+    return value;
+
+  float factor = std::pow(10, precision);
+  float integral;
+  float fractional = std::modf(value, &integral);
+  fractional = std::round(fractional * factor) / factor;
+  return integral + fractional;
+}
+
 gfx::Rect MathUtil::MapEnclosingClippedRect(const gfx::Transform& transform,
                                             const gfx::Rect& src_rect) {
   if (transform.IsIdentityOrIntegerTranslation()) {
     gfx::Vector2d offset(static_cast<int>(transform.matrix().getFloat(0, 3)),
                          static_cast<int>(transform.matrix().getFloat(1, 3)));
     return src_rect + offset;
   }
   gfx::RectF mapped_rect = MapClippedRect(transform, gfx::RectF(src_rect));
 
   // gfx::ToEnclosingRect crashes if called on a RectF with any NaN coordinate.
@@ skipping 756 matching lines @@
                         transform.matrix().getFloat(2, 0));
 }
 
 gfx::Vector3dF MathUtil::GetYAxis(const gfx::Transform& transform) {
   return gfx::Vector3dF(transform.matrix().getFloat(0, 1),
                         transform.matrix().getFloat(1, 1),
                         transform.matrix().getFloat(2, 1));
 }
 
 }  // namespace cc