Add GpuCommandBuffer support.

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index e2e27d586a029d0684b29bb5ec77175fe42ec8fa..9cce41c76da178efcbc836f8a0c23cc41914c9e1 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -101,6 +101,12 @@ public:
 
     void clearStencil(GrRenderTarget*) override;
 
+    GrGpuCommandBuffer* createCommandBuffer(const GrRenderTarget& target,
+                                            GrGpuCommandBuffer::LoadAndStoreOp colorOp,
+                                            GrColor colorClear,
+                                            GrGpuCommandBuffer::LoadAndStoreOp stencilOp,
+                                            GrColor stencilClear) override;
+
     void invalidateBoundRenderTarget() {
         fHWBoundRenderTargetUniqueID = SK_InvalidUniqueID;
     }