have raster-image return itself as a texture

src/image/SkImage_Base.h

Index: src/image/SkImage_Base.h
diff --git a/src/image/SkImage_Base.h b/src/image/SkImage_Base.h
index d31626764723bbf707aacc4f9e82f6235d612878..737b30d1db6e3736dcede3736d2bb23bc0bf09d0 100644
--- a/src/image/SkImage_Base.h
+++ b/src/image/SkImage_Base.h
@@ -56,7 +56,10 @@ public:
 
     // return a read-only copy of the pixels. We promise to not modify them,
     // but only inspect them (or encode them).
-    virtual bool getROPixels(SkBitmap*) const { return false; }
+    virtual bool getROPixels(SkBitmap*) const = 0;
+
+    // Caller must call unref when they are done.
+    virtual GrTexture* asTextureRef(GrContext*, SkImageUsageType) const = 0;
 
     virtual SkShader* onNewShader(SkShader::TileMode,
                                   SkShader::TileMode,
@@ -71,9 +74,6 @@ public:
 
     virtual bool onIsLazyGenerated() const { return false; }
 
-    // Caller must call unref when they are done.
-    virtual GrTexture* asTextureRef(GrContext*, SkImageUsageType) const { return nullptr; }
-
 private:
     const SkSurfaceProps fProps;