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..b6f1ceaa2de8610f81f1ce763c7e46ce9e3aabf2 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 IsMatrixApproximatelyPureTranslation(const SkMatrix44& matrix,

[danakj, 2013/10/15 15:34:35]

s/Pure//

[Dominik Grewe, 2013/10/15 17:04:19]

I think "Pure" was chosen to indicate that the matrix is a translation matrix
but nothing else (it doesn't have a scale, for example). I'm not the expert in
this area though, so I'm happy to change it. Just thought I'd double check.

+                                                   SkMScalar tolerance);
+  static bool IsMatrixApproximatelyIntegerTransform(const SkMatrix44& matrix,
+                                                    SkMScalar tolerance);
 };
 
 }  // namespace cc