Make default media device ID salts random by default

content/public/browser/resource_context.h

Index: content/public/browser/resource_context.h
diff --git a/content/public/browser/resource_context.h b/content/public/browser/resource_context.h
index 039ad94006ded4e49f25ad2a3784d3ed9d7e6b40..5d15160928ad529cdeaefd78e2e8f3d2c73ad072 100644
--- a/content/public/browser/resource_context.h
+++ b/content/public/browser/resource_context.h
@@ -72,11 +72,14 @@ class CONTENT_EXPORT ResourceContext : public base::SupportsUserData {
   // was put in place to fix http://crbug.com/341211 but I intend to
   // try to figure out how the lifetime should be fixed properly. The
   // original interface was just a method that returns a string.
-  //
-  // TODO(perkj): Make this method pure virtual when crbug/315022 is
-  // fixed.
   typedef base::Callback<std::string()> SaltCallback;
   virtual SaltCallback GetMediaDeviceIDSalt();
+
+  // Utility function useful for implementations
+  static std::string CreateRandomMediaDeviceIDSalt();

[jochen (gone - plz use gerrit), 2016/06/03 12:50:25]

as jam@ pointed out, you don't need to expose this method, embedders can just
call ResourceContext::GetMediaDeviceIDSalt()

[Guido Urdaneta, 2016/06/03 13:09:44]

The MediaDeviceIDSalt class uses that method to generate a random salt and store
it in preferences. This class does not know about ResourceContext, but it's used
by the profile implementation of ResourceContext.

If we don't expose it we need either to duplicate the method in
MediaDeviceIDSalt or do some less trivial refactoring in order to reuse the
ResourceContext method.
Since the utility method is almost a one-liner it's not such a big deal to
duplicate it. Are you OK with this?

+
+ private:
+  const std::string media_device_id_salt_;
 };
 
 }  // namespace content