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

content/browser/renderer_host/media/media_stream_dispatcher_host.h

Index: content/browser/renderer_host/media/media_stream_dispatcher_host.h
diff --git a/content/browser/renderer_host/media/media_stream_dispatcher_host.h b/content/browser/renderer_host/media/media_stream_dispatcher_host.h
index 805a7b0da604ebc6f0c670422f45f74e22f92ecf..a72d510bd365b2c480407cf06fcbff247b5d4c55 100644
--- a/content/browser/renderer_host/media/media_stream_dispatcher_host.h
+++ b/content/browser/renderer_host/media/media_stream_dispatcher_host.h
@@ -13,9 +13,12 @@
 #include "content/browser/renderer_host/media/media_stream_requester.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
+#include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_message_filter.h"
 
 namespace content {
+
+class BrowserContext;
 class MediaStreamManager;
 
 // MediaStreamDispatcherHost is a delegate for Media Stream API messages used by
@@ -25,6 +28,7 @@ class CONTENT_EXPORT MediaStreamDispatcherHost : public BrowserMessageFilter,
                                                  public MediaStreamRequester {
  public:
   MediaStreamDispatcherHost(int render_process_id,
+                            BrowserContext* browser_context,
                             MediaStreamManager* media_stream_manager);
 
   // MediaStreamRequester implementation.
@@ -95,6 +99,7 @@ class CONTENT_EXPORT MediaStreamDispatcherHost : public BrowserMessageFilter,
   StreamRequest PopRequest(const std::string& label);
 
   int render_process_id_;
+  ResourceContext* resource_context_;
   MediaStreamManager* media_stream_manager_;
 
   // Active requests. When the MediaStreamManager responds to a a request the