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

cc/base/math_util.cc

Index: cc/base/math_util.cc
diff --git a/cc/base/math_util.cc b/cc/base/math_util.cc
index 6e5ac0bd45db73b47d318a7d4b3aef0f42af0078..388fcd694eb4daed1a17cd6eb5b41ab41035ef9f 100644
--- a/cc/base/math_util.cc
+++ b/cc/base/math_util.cc
@@ -120,6 +120,21 @@ static inline void AddVertexToClippedQuad3d(const gfx::Point3F& new_vertex,
   (*num_vertices_in_clipped_quad)++;
 }
 
+float MathUtil::RoundToFixedPrecision(float value) {
+  const int kScalePrecision = 4;

[vmpstr, 2015/10/16 17:58:17]

Can you just write const float kFactor = 1e4 instead? And remove the dcheck?

Or better yet, take the precision as a parameter to this function.
MathUtil::RoundToFixedPrecision(foo) is not clear at all that it will round to 4
decimal places. (and why 4, btw?)

[prashant.n, 2015/10/17 01:28:13]

I'll add precision as a parameter, I was thinking to add this earlier, but then
thought of 3 digits fractional part is sufficient so let it be fixed value here.
4 is for having 3 digits fractional part, e.g. 3.336f for scale factor.

+  // Limiting precision 1 <= kScalePrecision <= 8, as floating point precision
+  // of >= 12 gives different values, 8 on a safer side.
+  DCHECK(kScalePrecision >= 1 && kScalePrecision <= 8);
+
+  const float factor = pow(10, kScalePrecision);
+  float integral;
+  float fractional = std::modf(value, &integral);
+  fractional *= factor;

[vmpstr, 2015/10/16 17:58:17]

nit: I'd just write these three things in one line

fractional = std::round(factor * fractional) / factor;

+  fractional = std::round(fractional);
+  fractional /= factor;
+  return integral + fractional;
+}
+
 gfx::Rect MathUtil::MapEnclosingClippedRect(const gfx::Transform& transform,
                                             const gfx::Rect& src_rect) {
   if (transform.IsIdentityOrIntegerTranslation()) {