Provide approximate type functions for SkMatrix44.

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 67a93709d0fe57efdc9d90d89466a665d268f4b6..00a358c63afc280cfedb42073a44f933a9042a88 100644
--- a/cc/base/math_util.h
+++ b/cc/base/math_util.h
@@ -177,6 +177,14 @@ class CC_EXPORT MathUtil {
   // 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);
+
+  // Check if matrices are of a certain type using approximate math. Each
+  // function gets a tolerance parameter to specify the maximum allowed
+  // absolute difference to the exact values.
+  static bool IsApproximatelyPureTranslation(

[danakj, 2013/10/16 19:04:14]

Thanks this API is more simple, how about moving this to the gfx::Transform()
class?

We already have IsIdentityOrTranslation() there. This would be
"IsApproximatelyIdentityOrTranslation(tolerance)".

The goal is to move everything in this class into ui/gfx/ and I don't see the
reason why we can't move this method there now instead of later.

+      const gfx::Transform& transform, SkMScalar tolerance);
+  static bool IsMatrixApproximatelyPureTranslation(

[danakj, 2013/10/16 19:04:14]

Drop this function from the public API, I think you can roll these two functions
into one.

+      const SkMatrix44& matrix, SkMScalar tolerance);
 };
 
 }  // namespace cc