Add function to get both min and max scale factors from matrix

include/core/SkMatrix.h

Index: include/core/SkMatrix.h
diff --git a/include/core/SkMatrix.h b/include/core/SkMatrix.h
index d52ab67f8c968896af88abd163356d232ed364f5..a594dac7551276f94302e1b9b85707b2be6e44f0 100644
--- a/include/core/SkMatrix.h
+++ b/include/core/SkMatrix.h
@@ -579,6 +579,13 @@ public:
     SkScalar getMaxScale() const;
 
     /**
+     * Gets both the min and max scale factors. The min scale factor is scaleFactors[0] and the max
+     * is scaleFactors[1]. If the matrix has perspective -1 will be returned and scaleFactors will

[reed1, 2014/05/20 15:17:55]

-1 --> false

[bsalomon, 2014/05/20 15:32:42]

Done.

+     * be unchanged.
+     */
+    bool getScaleFactors(SkScalar scaleFactors[2]) const;

[reed1, 2014/05/20 15:17:55]

1. do we need this entrypoint and the other two?
2. getMinMaxScaleFactors() ?

[bsalomon, 2014/05/20 15:32:42]

Most call sites only require 1 of the 2 and computing both can add an extra
branch and sqrt.
changed to getMinMaxScales() (to be consistent with getMinScale(),
getMaxScale())

+        
+    /**
      *  Return a reference to a const identity matrix
      */
     static const SkMatrix& I();