Chrome Cleaner: Remove indirect base::FilePath mojo dependency.

components/chrome_cleaner/public/typemaps/chrome_prompt_struct_traits.cc

+// Copyright 2017 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/chrome_cleaner/public/typemaps/chrome_prompt_struct_traits.h"
+
+namespace mojo {
+
+// static
+std::vector<uint16_t>
+StructTraits<chrome_cleaner::mojom::FilePathDataView, base::FilePath>::value(
+    const base::FilePath& file_path) {
+#if defined(OS_WIN)
+  return std::vector<uint16_t>(file_path.value().begin(),

[dcheng, 2017/06/13 23:45:35]

I have bad news... this gets called twice on serialization =/

(there's an open bug to consider fixing this, but it's gotten no traction...)

Two alternatives:
1. Have this return a CArray / ConstCArray which avoids copying the memory.
2. Use SetUpContext/TearDownContext() to create the vector once per
serialization, and return a reference to it here.

I'd probably go with (1) here.

[proberge, 2017/06/14 14:13:58]

Done.

+                               file_path.value().end());
+#else
+  NOTREACHED();
+  return std::vector<uint16_t>();
+#endif
+}
+
+// static
+bool StructTraits<chrome_cleaner::mojom::FilePathDataView,
+                  base::FilePath>::Read(chrome_cleaner::mojom::FilePathDataView
+                                            path_view,
+                                        base::FilePath* out) {
+#if defined(OS_WIN)
+  ArrayDataView<uint16_t> view;
+  path_view.GetValueDataView(&view);
+  base::FilePath path = base::FilePath(base::string16(
+      reinterpret_cast<const base::char16*>(view.data()), view.size()));

[ftirelo, 2017/06/13 23:29:29]

Nit: could we use base::FilePath::StringType::value_type instead of base::char16
?

[proberge, 2017/06/14 14:13:58]

Maybe. Is this so we can remove the defined(OS_WIN)? I don't think we'll ever
need to implement this method for non-Windows OSes. 

+  *out = std::move(path);
+  return true;
+#else
+  NOTREACHED();
+  return false;
+#endif
+}
+
+}  // namespace mojo