Let Contraints Controll Mute/Unmute Audio Local Playback For Desktop Sharing

content/public/browser/desktop_media_id.cc

Index: content/public/browser/desktop_media_id.cc
diff --git a/content/public/browser/desktop_media_id.cc b/content/public/browser/desktop_media_id.cc
index 8a20598af67f82db03a1dffad8601597df05d1c3..6c0027d40ad65bfdaf8f646d5a849ab1328834e4 100644
--- a/content/public/browser/desktop_media_id.cc
+++ b/content/public/browser/desktop_media_id.cc
@@ -129,8 +129,8 @@ bool DesktopMediaID::operator==(const DesktopMediaID& other) const {
 //                         window:"window_id:aura_id".

[dcheng, 2016/09/16 22:36:04]

It doesn't have to be done in this CL... but can we use something more
structured than a std::string to transport this information? While I think the
current parsing code is safe, it'd make it even easier if I didn't have to read
any parsing code =)

[qiangchen, 2016/09/16 22:45:52]

Good suggestion. But I think one reason we use string is that when we first
wrote the media code, we support camera, microphone etc, and their device_ids
are strings we got from OS. Later when we add desktop capture functionality, we
made up some format to represent those IDs, to avoid changing all the parameter
signatures along the code paths.

 DesktopMediaID DesktopMediaID::Parse(const std::string& str) {
   // For WebContents type.
-  WebContentsMediaCaptureId web_id = WebContentsMediaCaptureId::Parse(str);
-  if (!web_id.is_null())
+  WebContentsMediaCaptureId web_id;
+  if (WebContentsMediaCaptureId::Parse(str, &web_id))
     return DesktopMediaID(TYPE_WEB_CONTENTS, 0, web_id);
 
   // For screen and window types.