Make default media device ID salts random by default

content/shell/browser/shell_browser_context.h

Index: content/shell/browser/shell_browser_context.h
diff --git a/content/shell/browser/shell_browser_context.h b/content/shell/browser/shell_browser_context.h
index 3f2f502bf2c43c020407f8cbcb81a5cc0d420801..794330e89096d3f6874bbe2a4e9aef041dd91c5a 100644
--- a/content/shell/browser/shell_browser_context.h
+++ b/content/shell/browser/shell_browser_context.h
@@ -6,6 +6,7 @@
 #define CONTENT_SHELL_BROWSER_SHELL_BROWSER_CONTEXT_H_
 
 #include <memory>
+#include <string>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
@@ -75,13 +76,15 @@ class ShellBrowserContext : public BrowserContext {
     // ResourceContext implementation:
     net::HostResolver* GetHostResolver() override;
     net::URLRequestContext* GetRequestContext() override;
+    SaltCallback GetMediaDeviceIDSalt() override;
 
     void set_url_request_context_getter(ShellURLRequestContextGetter* getter) {
       getter_ = getter;
     }
 
-  private:
+   private:
     ShellURLRequestContextGetter* getter_;
+    std::string media_device_id_salt_;
 
     DISALLOW_COPY_AND_ASSIGN(ShellResourceContext);
   };