Implement a salt for MediaSource IDs that can be cleared by a user.

content/public/browser/content_browser_client.h

Index: content/public/browser/content_browser_client.h
diff --git a/content/public/browser/content_browser_client.h b/content/public/browser/content_browser_client.h
index dc7f9dd057c29299d8e8a4a4cd2ce5330f2fe460..fa98218a17443dc4c0a693c404885e030d1390b6 100644
--- a/content/public/browser/content_browser_client.h
+++ b/content/public/browser/content_browser_client.h
@@ -524,6 +524,11 @@ class CONTENT_EXPORT ContentBrowserClient {
   // else we should do with the file.
   virtual std::string GetDefaultDownloadName();
 
+  // Returns a random salt string that is used for creating MediaSourceIds.
+  // The salt should depend on the current user profile and should be reset if
+  // the cache is cleared. This is called on the IO thread.

[Jói, 2013/10/31 16:14:47]

Is clearing the cache the right trigger? This is more or less equivalent to a
persistent cookie so I would have thought "when cookies are cleared".

[perkj_chrome, 2013/10/31 17:05:44]

right - that is what I actually do...

+  virtual std::string GetDeviceIdSalt(ResourceContext* rc);
+
   // Notification that a pepper plugin has just been spawned. This allows the
   // embedder to add filters onto the host to implement interfaces.
   // This is called on the IO thread.