mojo: Mark DataView readers as WARN_UNUSED_RESULT.

components/arc/bluetooth/bluetooth_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 "components/arc/bluetooth/bluetooth_struct_traits.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/strings/string_number_conversions.h"
@@ skipping 16 matching lines @@
 }
 
 }  // namespace
 
 namespace mojo {
 
 // static
 std::vector<uint8_t>
 StructTraits<arc::mojom::BluetoothUUIDDataView, device::BluetoothUUID>::uuid(
     const device::BluetoothUUID& input) {
+  // TODO(dcheng): Figure out what to do here, this is called twice on
+  // serialization. Building a vector is a little inefficient.
   std::string uuid_str = StripNonHex(input.canonical_value());
 
   std::vector<uint8_t> address_bytes;
   base::HexStringToBytes(uuid_str, &address_bytes);
   return address_bytes;
 }
 
 // static
 bool StructTraits<arc::mojom::BluetoothUUIDDataView,
                   device::BluetoothUUID>::Read(
     arc::mojom::BluetoothUUIDDataView data,
     device::BluetoothUUID* output) {
   std::vector<uint8_t> address_bytes;
-  data.ReadUuid(&address_bytes);
+  if (!data.ReadUuid(&address_bytes))
+    return false;
 
   if (address_bytes.size() != kUUIDSize)
     return false;
 
   // BluetoothUUID expects the format below with the dashes inserted.
   // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
   std::string uuid_str =
       base::HexEncode(address_bytes.data(), address_bytes.size());
   constexpr size_t kUuidDashPos[] = {8, 13, 18, 23};
   for (auto pos : kUuidDashPos)
     uuid_str = uuid_str.insert(pos, "-");
 
   device::BluetoothUUID result(uuid_str);
 
   DCHECK(result.IsValid());
   *output = result;
   return true;
 }
 
 }  // namespace mojo