CopyOutputRequest must have a working result_callback_ when received over mojo

cc/ipc/copy_output_request_struct_traits.cc

Index: cc/ipc/copy_output_request_struct_traits.cc
diff --git a/cc/ipc/copy_output_request_struct_traits.cc b/cc/ipc/copy_output_request_struct_traits.cc
index 3985ba41eb744a7c114458b4bc94e1c8b26ce9b8..c33d4196668438aa6126a5b08eee2e87896f9ba7 100644
--- a/cc/ipc/copy_output_request_struct_traits.cc
+++ b/cc/ipc/copy_output_request_struct_traits.cc
@@ -4,9 +4,50 @@
 
 #include "cc/ipc/copy_output_request_struct_traits.h"
 
+#include "mojo/public/cpp/bindings/strong_binding.h"
+
+namespace {
+
+// When we're sending a CopyOutputRequest, we keep the result_callback_ in a
+// CopyOutputResultSenderImpl and send a CopyOutputResultSenderPtr to the other
+// process. When SendResult is called, we run the stored result_callback_.
+class CopyOutputResultSenderImpl : public cc::mojom::CopyOutputResultSender {
+ public:
+  CopyOutputResultSenderImpl(
+      cc::CopyOutputRequest::CopyOutputRequestCallback result_callback)
+      : result_callback_(result_callback) {}
+
+  // mojom::TextureMailboxReleaser implementation:
+  void SendResult(std::unique_ptr<cc::CopyOutputResult> result) override {
+    result_callback_.Run(std::move(result));

[danakj, 2017/02/15 17:19:57]

Can you also make sure this is called only once and called when the pipe breaks
with an empty result? That is what the copy request destructor would do.

Can you also test those cases?

[Saman Sami, 2017/02/15 17:36:50]

Will do. It's hard to test though because I have no way of accessing the
interface pointer in the unit tests. It's wrapped in a base::Callback and and
the callback is hidden inside a CopyOutputRequest, and CopyOutputRequest
automatically takes care of everything you said.

[danakj, 2017/02/15 17:41:59]

Can you instantiate the CopyOutputResultSenderPtr from result_sender() directly
in the test to use it?

[Saman Sami, 2017/02/15 17:51:42]

Yeah I think you're actually right.

+  }
+
+ private:
+  cc::CopyOutputRequest::CopyOutputRequestCallback result_callback_;
+};
+
+void SendResult(cc::mojom::CopyOutputResultSenderPtr ptr,
+                std::unique_ptr<cc::CopyOutputResult> result) {
+  ptr->SendResult(std::move(result));
+}
+
+}  // namespace
+
 namespace mojo {
 
 // static
+cc::mojom::CopyOutputResultSenderPtr
+StructTraits<cc::mojom::CopyOutputRequestDataView,
+             std::unique_ptr<cc::CopyOutputRequest>>::
+    result_sender(const std::unique_ptr<cc::CopyOutputRequest>& request) {
+  cc::mojom::CopyOutputResultSenderPtr result_sender;
+  auto impl = base::MakeUnique<CopyOutputResultSenderImpl>(
+      std::move(request->result_callback_));
+  MakeStrongBinding(std::move(impl), MakeRequest(&result_sender));
+  return result_sender;
+}
+
+// static
 bool StructTraits<cc::mojom::CopyOutputRequestDataView,
                   std::unique_ptr<cc::CopyOutputRequest>>::
     Read(cc::mojom::CopyOutputRequestDataView data,
@@ -24,6 +65,11 @@ bool StructTraits<cc::mojom::CopyOutputRequestDataView,
   if (!data.ReadTextureMailbox(&request->texture_mailbox_))
     return false;
 
+  auto result_sender =
+      data.TakeResultSender<cc::mojom::CopyOutputResultSenderPtr>();
+  request->result_callback_ =
+      base::Bind(SendResult, base::Passed(&result_sender));
+
   *out_p = std::move(request);
 
   return true;