Add logic to GLRenderer to support RenderPassDrawQuad copying.

cc/output/software_renderer.h

Index: cc/output/software_renderer.h
diff --git a/cc/output/software_renderer.h b/cc/output/software_renderer.h
index c7e0f809d43fd3171f34b0f069b3e115ebfb16d4..ba0342a641d6ecb1269eae152aa56e8cb2467bce 100644
--- a/cc/output/software_renderer.h
+++ b/cc/output/software_renderer.h
@@ -106,6 +106,12 @@ class CC_EXPORT SoftwareRenderer : public DirectRenderer {
       const RenderPassDrawQuad* quad,
       SkShader::TileMode content_tile_mode) const;
 
+  // RenderPassDrawQuadCopier
+  bool CopyRenderPassDrawQuadToIOSurface(const RenderPassDrawQuad* quad,
+                                         ResourceId* resource_id) override;
+  void ReleaseIOSurfaces(const std::vector<ResourceId>& resources) override;
+  void UpdateCopyCountForFrame(size_t count) override;
+
   bool disable_picture_quad_image_filtering_ = false;
 
   RendererCapabilitiesImpl capabilities_;