Add IPC to query capabilities of video input devices.

content/browser/media/media_devices_util.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 "content/browser/media/media_devices_util.h"
+
+#include <utility>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_tokenizer.h"
+#include "content/browser/frame_host/render_frame_host_delegate.h"
+#include "content/browser/frame_host/render_frame_host_impl.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/common/media_stream_request.h"
+#include "media/base/media_switches.h"
+
+namespace content {
+
+namespace {
+
+std::string GetDefaultMediaDeviceIDOnUIThread(MediaDeviceType device_type,
+                                              int render_process_id,
+                                              int render_frame_id) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  RenderFrameHostImpl* frame_host =
+      RenderFrameHostImpl::FromID(render_process_id, render_frame_id);
+  if (!frame_host)
+    return std::string();
+
+  RenderFrameHostDelegate* delegate = frame_host->delegate();
+  if (!delegate)
+    return std::string();
+
+  MediaStreamType media_stream_type;
+  switch (device_type) {
+    case MEDIA_DEVICE_TYPE_AUDIO_INPUT:
+      media_stream_type = MEDIA_DEVICE_AUDIO_CAPTURE;
+      break;
+    case MEDIA_DEVICE_TYPE_VIDEO_INPUT:
+      media_stream_type = MEDIA_DEVICE_VIDEO_CAPTURE;
+      break;
+    default:
+      return std::string();
+  }
+
+  return delegate->GetDefaultMediaDeviceID(media_stream_type);
+}
+
+std::string GetDefaultMediaDeviceIDFromCommandLine(
+    MediaDeviceType device_type) {
+  DCHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kUseFakeDeviceForMediaStream));
+  const std::string option =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kUseFakeDeviceForMediaStream);
+  // Optional comma delimited parameters to the command line can specify values
+  // for the default device IDs.
+  // Examples: "video-input-default-id=mycam, audio-input-default-id=mymic"
+  base::StringTokenizer option_tokenizer(option, ", ");
+  option_tokenizer.set_quote_chars("\"");
+
+  while (option_tokenizer.GetNext()) {
+    std::vector<std::string> param =
+        base::SplitString(option_tokenizer.token(), "=", base::TRIM_WHITESPACE,
+                          base::SPLIT_WANT_NONEMPTY);
+    if (param.size() != 2u) {
+      LOG(WARNING) << "Forget a value '" << option << "'? Use name=value for "
+                   << switches::kUseFakeDeviceForMediaStream << ".";

[dcheng, 2017/01/20 07:56:50]

DLOG. This doesn't seem like a switch real users are going to use.

[Guido Urdaneta, 2017/01/20 12:40:58]

Done.

+      return std::string();
+    }
+
+    if (device_type == MEDIA_DEVICE_TYPE_AUDIO_INPUT &&
+        base::EqualsCaseInsensitiveASCII(param.front(),

[dcheng, 2017/01/20 07:56:50]

Similarly, since this isn't really exposed to real users, I think a simple
comparison should suffice. *shrug*

[Guido Urdaneta, 2017/01/20 12:40:58]

Done.

+                                         "audio-input-default-id")) {
+      return param.back();
+    } else if (device_type == MEDIA_DEVICE_TYPE_VIDEO_INPUT &&
+               base::EqualsCaseInsensitiveASCII(param.front(),
+                                                "video-input-default-id")) {
+      return param.back();
+    }
+  }
+
+  return std::string();
+}
+
+}  // namespace
+
+void GetDefaultMediaDeviceID(
+    MediaDeviceType device_type,
+    int render_process_id,
+    int render_frame_id,
+    const base::Callback<void(const std::string&)>& callback) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kUseFakeDeviceForMediaStream)) {
+    callback.Run(GetDefaultMediaDeviceIDFromCommandLine(device_type));
+    return;
+  }
+
+  BrowserThread::PostTaskAndReplyWithResult(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&GetDefaultMediaDeviceIDOnUIThread, device_type,
+                 render_process_id, render_frame_id),
+      callback);
+}
+
+}  // namespace content