[Presentation API] Add support for multiple URLs in PresentationRequest on Media Router UI side

chrome/browser/ui/webui/media_router/cast_modes_with_media_sources.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 "base/stl_util.h"
+#include "chrome/browser/ui/webui/media_router/cast_modes_with_media_sources.h"
+
+namespace media_router {
+
+CastModesWithMediaSources::CastModesWithMediaSources() {}
+CastModesWithMediaSources::CastModesWithMediaSources(
+    const CastModesWithMediaSources& other) = default;
+CastModesWithMediaSources::~CastModesWithMediaSources() {}
+
+void CastModesWithMediaSources::AddSource(
+    MediaCastMode cast_mode, const MediaSource& source) {
+  cast_modes_[cast_mode].insert(source);
+}
+
+void CastModesWithMediaSources::RemoveSource(
+    MediaCastMode cast_mode, const MediaSource& source) {
+  cast_modes_[cast_mode].erase(source);

[mark a. foltz, 2016/09/09 22:22:26]

I would use .find() here so you don't have to allocate and immediately erase
an empty entry when there's no |cast_mode| in the map.

[takumif, 2016/09/13 03:48:21]

Done.

+  if (cast_modes_[cast_mode].empty())
+    cast_modes_.erase(cast_mode);
+}
+
+bool CastModesWithMediaSources::HasSource(
+    MediaCastMode cast_mode, const MediaSource& source) const {
+  return base::ContainsKey(cast_modes_, cast_mode)

[mark a. foltz, 2016/09/09 22:22:26]

Using .find() would avoid a double lookup in cast_modes_.

e.g. something like:

const auto cast_modes_it = cast_modes_.find(cast_mode);
return cast_modes_it != cast_modes_.end() ? ContainsKey(cast_modes_it->second,
source) : false;

[takumif, 2016/09/13 03:48:21]

Given the low number of cast modes, I think I prefer using ContainsKey twice for
readability.

[mark a. foltz, 2016/09/13 17:30:15]

There are at most 3, IIUC. It would be just as fast if not faster for
|cast_modes_| to be a vector, but then you'd need to define a struct to hold the
MediaCastMode.  Doesn't seem worth adding code and allocating extra objects for
a small optimization.

[takumif, 2016/09/13 19:20:34]

Acknowledged.

+             ? base::ContainsKey(cast_modes_.at(cast_mode), source)
+             : false;
+}
+
+CastModeSet CastModesWithMediaSources::GetCastModes() const {
+  CastModeSet cast_mode_set;
+  for (const auto& cast_mode_pair : cast_modes_)
+    cast_mode_set.insert(cast_mode_pair.first);
+  return cast_mode_set;
+}
+
+bool CastModesWithMediaSources::IsEmpty() const {
+  return cast_modes_.empty();
+}
+
+}  // namespace media_router