Add basic SVD support to SkMatrix. Allows you to pull out the x- and y-scale factors, sandwiched by…

include/core/SkMatrix.h

Index: include/core/SkMatrix.h
diff --git a/include/core/SkMatrix.h b/include/core/SkMatrix.h
index f148e390b5cd4930f2d985f61a286cda3748b7cc..80ef9cb3f6266958bfb421e086efd3407c1e304e 100644
--- a/include/core/SkMatrix.h
+++ b/include/core/SkMatrix.h
@@ -96,6 +96,16 @@ public:
      */
     bool preservesRightAngles(SkScalar tol = SK_ScalarNearlyZero) const;
 
+    /** Decomposes the upper 2x2 of the matrix into a rotation, followed by a non-uniform scale, 
+        followed by another rotation. Returns true if successful.
+        If the scale factors are uniform, then rotation1 will be 0.
+        If there is a reflection, yScale will be negative.
+        Returns false if the matrix is degenerate.

[reed1, 2013/07/18 14:15:54]

... or perspective?

+     */
+    bool decomposeUpper2x2(SkScalar* rotation0, 
+                           SkScalar* xScale, SkScalar* yScale, 
+                           SkScalar* rotation1) const;
+
     enum {
         kMScaleX,
         kMSkewX,