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

cc/base/math_util.h

Index: cc/base/math_util.h
diff --git a/cc/base/math_util.h b/cc/base/math_util.h
index a83ab4fdce34be03b56fd23ffe978262abbe69fb..ad7f508a38993b01ec2aa3cd5f6b8b89ccf56634 100644
--- a/cc/base/math_util.h
+++ b/cc/base/math_util.h
@@ -96,6 +96,10 @@ class CC_EXPORT MathUtil {
   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>