Use surface copy requests for layout tests.

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 8a771c9ee7bfb6aad650489888624ebfcc58670b..7f781534ca520bafea43659f771a87c611d589c8 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -23,6 +23,7 @@
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_synthetic_delay.h"
 #include "build/build_config.h"
+#include "cc/output/copy_output_request.h"
 #include "cc/output/output_surface.h"
 #include "cc/scheduler/begin_frame_source.h"
 #include "components/scheduler/renderer/render_widget_scheduling_state.h"
@@ -817,6 +818,12 @@ void RenderWidget::WillBeginCompositorFrame() {
                     WillBeginCompositorFrame());
 }
 
+std::unique_ptr<cc::SwapPromise> RenderWidget::RequestCopyOfOutputForLayoutTest(
+    std::unique_ptr<cc::CopyOutputRequest> request) {
+  return RenderThreadImpl::current()->RequestCopyOfOutputForLayoutTest(
+      routing_id_, std::move(request));
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // RenderWidgetInputHandlerDelegate