remove getter for imagegenerator factory, update test

include/core/SkImageGenerator.h

Index: include/core/SkImageGenerator.h
diff --git a/include/core/SkImageGenerator.h b/include/core/SkImageGenerator.h
index 46001c85370755ef69e28f2cc9f842268815ddcf..2d71b4036d99e4fbc2e4ba9080a0b880ebbd4717 100644
--- a/include/core/SkImageGenerator.h
+++ b/include/core/SkImageGenerator.h
@@ -221,6 +221,8 @@ protected:
 private:
     const SkImageInfo fInfo;
 
+    // This is our default impl, which may be different on different platforms.
+    // It is called from NewFromEncoded() after it has checked for any runtime factory.

[scroggo, 2015/07/09 19:22:57]

Looks good, although I was thinking it could have a hint that the implementation
need not check for a null SkData.

     static SkImageGenerator* NewFromEncodedImpl(SkData*);
 };