[Media Router] Clean up issues related code.

chrome/browser/media/router/mojo/media_router_struct_traits.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/media/router/mojo/media_router_struct_traits.h"
+
+namespace mojo {
+
+// static
+bool StructTraits<media_router::mojom::IssueDataView, media_router::IssueInfo>::
+    Read(media_router::mojom::IssueDataView data,
+         media_router::IssueInfo* out) {
+  if (!data.ReadTitle(&out->title))
+    return false;
+
+  media_router::mojom::Issue::ActionType default_action;

[dcheng, 2016/12/12 20:59:56]

I think you can avoid the manual calls to EnumTraits by using the C++ enum type
here instead of the mojo enum type as well.

[imcheng, 2016/12/12 22:40:01]

I am not sure how we can set out->default_action without a C++ value here
otherwise. Do you have some examples?

[dcheng, 2016/12/13 00:46:38]

I think it should Just Work if typemapped; my recollection is the ReadX(...)
helpers are templated, and will figure out how the right thing.

[imcheng, 2016/12/13 00:51:45]

Thanks -- using ReadX() worked.

+  if (!data.ReadDefaultAction(&default_action))
+    return false;
+
+  if (!EnumTraits<
+          media_router::mojom::Issue::ActionType,
+          media_router::IssueInfo::Action>::FromMojom(default_action,
+                                                      &out->default_action))
+    return false;
+
+  media_router::mojom::Issue::Severity severity;
+  if (!data.ReadSeverity(&severity))
+    return false;
+
+  if (!EnumTraits<media_router::mojom::Issue::Severity,
+                  media_router::IssueInfo::Severity>::FromMojom(severity,
+                                                                &out->severity))
+    return false;
+
+  base::Optional<std::string> message;
+  if (!data.ReadMessage(&message))
+    return false;
+
+  out->message = message.value_or(std::string());
+
+  base::Optional<std::vector<media_router::mojom::Issue::ActionType>>
+      secondary_actions;
+  if (!data.ReadSecondaryActions(&secondary_actions))
+    return false;
+
+  if (secondary_actions.has_value()) {
+    for (const auto action : secondary_actions.value()) {
+      media_router::IssueInfo::Action converted_action;
+      if (!EnumTraits<
+              media_router::mojom::Issue::ActionType,
+              media_router::IssueInfo::Action>::FromMojom(action,
+                                                          &converted_action))
+        return false;
+      out->secondary_actions.push_back(converted_action);
+    }
+  }
+
+  base::Optional<std::string> route_id;
+  if (!data.ReadRouteId(&route_id))
+    return false;
+
+  out->route_id = route_id.value_or(std::string());
+
+  out->is_blocking = data.is_blocking();
+  out->help_page_id = data.help_page_id();
+
+  return true;
+}
+
+}  // namespace mojo