Remove support for GL discards

src/gpu/gl/GrGLGpuCommandBuffer.h

Index: src/gpu/gl/GrGLGpuCommandBuffer.h
diff --git a/src/gpu/gl/GrGLGpuCommandBuffer.h b/src/gpu/gl/GrGLGpuCommandBuffer.h
index 0591ffde3bf31eab2d25e6d1c68800e1ac49f2d5..c5f0eea4ff3ff6f9de2e9c46e1ad2b70d23aef15 100644
--- a/src/gpu/gl/GrGLGpuCommandBuffer.h
+++ b/src/gpu/gl/GrGLGpuCommandBuffer.h
@@ -25,7 +25,7 @@ public:
 
     void end() override {}
 
-    void discard(GrRenderTarget* rt) override { fGpu->discard(rt); }
+    void discard(GrRenderTarget* rt) override {}
 
 private:
     GrGpu* gpu() override { return fGpu; }