Add wrapBackendTextureAsRenderTarget API

include/core/SkSurface.h

Index: include/core/SkSurface.h
diff --git a/include/core/SkSurface.h b/include/core/SkSurface.h
index 45262d78e63d3d30351c43ccd22ae3c2442ad0a3..5c3ef209745641b47cb36244f7cea186b6995140 100644
--- a/include/core/SkSurface.h
+++ b/include/core/SkSurface.h
@@ -108,7 +108,6 @@ public:
         return NewFromBackendTexture(ctx, desc, props);
     }
 
-
     /**
      *  Used to wrap a pre-existing 3D API rendering target as a SkSurface. Skia will not assume
      *  ownership of the render target and the client must ensure the render target is valid for the
@@ -118,6 +117,17 @@ public:
                                                  const SkSurfaceProps*);
 
     /**
+     *  Used to wrap a pre-existing 3D API texture as a SkSurface. Skia will treat the texture as
+     *  a rendering target only, but unlike NewFromBackendRenderTarget, Skia will manage and own
+     *  the associated render target objects (but not the provided texture). The kRenderTarget flag
+     *  must be set on GrBackendTextureDesc for this to succeed. Skia will not assume ownership
+     *  of the texture and the client must ensure the texture is valid for the lifetime of the
+     *  SkSurface.
+     */
+    static SkSurface* NewFromBackendTextureAsRenderTarget(
+            GrContext*, const GrBackendTextureDesc&, const SkSurfaceProps*);
+
+    /**
      *  Return a new surface whose contents will be drawn to an offscreen
      *  render target, allocated by the surface.
      *
@@ -280,6 +290,11 @@ public:
 
     const SkSurfaceProps& props() const { return fProps; }
 
+    /**
+     * Issue any pending surface IO to the current backend 3D API and resolve any surface MSAA.
+     */
+    void prepareForExternalIO();
+
 protected:
     SkSurface(int width, int height, const SkSurfaceProps*);
     SkSurface(const SkImageInfo&, const SkSurfaceProps*);