Remove unused SkImage_Base and SkImage_Gpu onNewSurface methods

src/image/SkImage_Gpu.h

Index: src/image/SkImage_Gpu.h
diff --git a/src/image/SkImage_Gpu.h b/src/image/SkImage_Gpu.h
index a9d9c33f2d00cd0c3f193082f97b472631fd55c4..02260bcca5d3c17bf0d6a38ebfbf723dea31aec3 100644
--- a/src/image/SkImage_Gpu.h
+++ b/src/image/SkImage_Gpu.h
@@ -51,10 +51,6 @@ public:
     bool onReadPixels(const SkImageInfo&, void* dstPixels, size_t dstRowBytes,
                       int srcX, int srcY, CachingHint) const override;
 
-    sk_sp<SkSurface> onNewSurface(const SkImageInfo& info) const override {
-        return SkSurface::MakeRenderTarget(fTexture->getContext(), SkBudgeted::kNo, info);
-    }
-
 private:
     SkAutoTUnref<GrTexture>     fTexture;
     const SkAlphaType           fAlphaType;