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

cc/base/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_BASE_MATH_UTIL_H_
 #define CC_BASE_MATH_UTIL_H_
 
 #include <algorithm>
 #include <cmath>
 #include <vector>
@@ skipping 78 matching lines @@
 
   static float Deg2Rad(float deg) { return deg * kPiFloat / 180.0f; }
   static float Rad2Deg(float rad) { return rad * 180.0f / kPiFloat; }
 
   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);
   }
+  // Round the given float value to fixed precision. This makes amlost euqal
+  // floats (differ by some threshold magnitude of floating point epsilon) to
+  // be considered as same.
+  static float RoundToFixedPrecision(float value);
 
   // Returns true if rounded up value does not overflow, false otherwise.
   template <typename T>
   static bool VerifyRoundup(T n, T mul) {
     return mul && (n <= (std::numeric_limits<T>::max() -
                          (std::numeric_limits<T>::max() % mul)));
   }
 
   // Rounds up a given |n| to be a multiple of |mul|, but may overflow.
   // Examples:
@@ skipping 207 matching lines @@
   template <typename T>
   static T RoundDownInternal(T n, T mul) {
     return (n > 0) ? (n / mul) * mul : (n == 0) ? 0
                                                 : ((n - mul + 1) / mul) * mul;
   }
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_MATH_UTIL_H_