Mojo C++ bindings: make String16 and gfx::Size available in Blink

mojo/common/common_custom_types_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 "mojo/common/common_custom_types_struct_traits.h"
 
 #include <iterator>
 
 namespace mojo {
 
 // static
+std::vector<uint16_t>
+StructTraits<mojo::common::mojom::String16DataView, base::string16>::data(
+    const base::string16& str) {
+  return std::vector<uint16_t>(str.data(), str.data() + str.size());
+}
+
+// static
+bool StructTraits<mojo::common::mojom::String16DataView, base::string16>::Read(
+    mojo::common::mojom::String16DataView data,
+    base::string16* out) {
+  std::vector<uint16_t> raw_data;
+  if (!data.ReadData(&raw_data))

[Ken Rockot(use gerrit already), 2016/10/04 06:28:40]

To esprehn@'s point, you can do:

  mojo::ArrayDataView<int16_t> view;
  data.GetDataDataView(&view);
  out->assign(view.data(), view.size());

[Zhiqiang Zhang (Slow), 2016/10/04 10:07:18]

Hmm, seems like I can do something similar to
"mojo/public/cpp/bindings/string_traits_string16.h".
Maybe it's also better to put the struct traits file there?
Will send back for review after I finished.

[Zhiqiang Zhang (Slow), 2016/10/04 13:21:59]

OK, I decided not to do that.
I found that StringTraits are used for converting custom strings to/from UTF8,
which will bring extra overhead for base::string16.

Now I'm just avoiding making redundant copies as you suggested.

BTW, just FYI to rockot@. I guess string_traits_string16 should be removed now?
However I cannot remove it at the moment since I see a lot of uses of
StringTraits<base::string16> for implicitly mapping base::string16 into mojo
string (8-bit), which I'm not sure if it's abusing or not. For example
https://cs.chromium.org/chromium/src/components/autofill/content/public/inter...
autofill.mojom.FormData::name is mojo string but it's base::string16 in
autofill::FormData.

+    return false;
+  out->assign(reinterpret_cast<base::char16*>(raw_data.data()),
+              raw_data.size());
+  return true;
+}
+
+// static
 const std::vector<uint32_t>&
 StructTraits<mojo::common::mojom::VersionDataView, base::Version>::components(
     const base::Version& version) {
   return version.components();
 }
 
 // static
 bool StructTraits<mojo::common::mojom::VersionDataView, base::Version>::Read(
     mojo::common::mojom::VersionDataView data,
     base::Version* out) {
@@ skipping 15 matching lines @@
 
   // Receiving a zeroed UnguessableToken is a security issue.
   if (high == 0 && low == 0)
     return false;
 
   *out = base::UnguessableToken::Deserialize(high, low);
   return true;
 }
 
 }  // namespace mojo