Move SkMatrixImageFilter into core, and add a factory fn for it.

include/core/SkImageFilter.h

Index: include/core/SkImageFilter.h
diff --git a/include/core/SkImageFilter.h b/include/core/SkImageFilter.h
index b64a2957fdf993826acc863997a95811ebc8a611..92590162168e3fa729dc867793fdb3bcda89b84c 100644
--- a/include/core/SkImageFilter.h
+++ b/include/core/SkImageFilter.h
@@ -8,6 +8,7 @@
 #ifndef SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
+#include "SkFilterQuality.h"
 #include "SkFlattenable.h"
 #include "SkMatrix.h"
 #include "SkRect.h"
@@ -192,6 +193,13 @@ public:
     // Default impl returns union of all input bounds.
     virtual void computeFastBounds(const SkRect&, SkRect*) const;
 
+    /**
+     * Create an SkMatrixImageFilter, which transforms its input by the given matrix.
+     */
+    static SkImageFilter* CreateMatrix(const SkMatrix& matrix,

[Stephen White, 2015/03/19 18:47:42]

BTW, I was thinking of changing this to CreateMatrixFilter(), since
CreateMatrix() is somewhat ambiguous. CreateMatrixImageFilter() seems a bit
long, but I could go with that too.

[reed1, 2015/03/19 20:50:01]

Agreed, CreateMatrixFilter is more consistent with other std factories in
SkColorFilter and SkShader.

+                                       SkFilterQuality,
+                                       SkImageFilter* input = NULL);
+
 #if SK_SUPPORT_GPU
     /**
      * Wrap the given texture in a texture-backed SkBitmap.