When a bitmap is texture-backed, change SkBitmap::copyTo() to do a deep
copy of the texels in VRAM rather than a readback and re-upload.  This
gives a 3-10X speedup on recursive canvas-to-canvas draws.

N.B.:  This introduces a new GM test, which will need new baselines.



git-svn-id: http://skia.googlecode.com/svn/trunk@2790 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index bc52159..5b48c0b 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -548,6 +548,12 @@
                                          config, buffer, rowBytes, 0);
     }
     /**
+     * Copies all texels from one texture to another.
+     * @param src           the texture to copy from.
+     * @param dst           the render target to copy to.
+     */
+    void copyTexture(GrTexture* src, GrRenderTarget* dst);
+    /**
      * Applies a 1D convolution kernel in the X direction to a rectangle of
      * pixels from a given texture.
      * @param texture         the texture to read from