Move chrome-specific SerializedNavigation code to chrome/.

components/sessions/content/content_serialized_navigation_driver.h

Index: components/sessions/content/content_serialized_navigation_driver.h
diff --git a/components/sessions/content/content_serialized_navigation_driver.h b/components/sessions/content/content_serialized_navigation_driver.h
index 768300dd1c8385a8b52d56c1ab00c32eb2b2f94f..ec732a707661378a6e30f9ce3bff6bcbbe964fa4 100644
--- a/components/sessions/content/content_serialized_navigation_driver.h
+++ b/components/sessions/content/content_serialized_navigation_driver.h
@@ -5,14 +5,13 @@
 #ifndef COMPONENTS_SESSIONS_CONTENT_CONTENT_SERIALIZED_NAVIGATION_DRIVER_H_
 #define COMPONENTS_SESSIONS_CONTENT_CONTENT_SERIALIZED_NAVIGATION_DRIVER_H_
 
-#include "components/sessions/core/serialized_navigation_driver.h"
-
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "components/sessions/content/extended_info_handler.h"
+#include "components/sessions/core/serialized_navigation_driver.h"
 #include "components/sessions/core/sessions_export.h"
 
 namespace base {
@@ -32,6 +31,9 @@ class SESSIONS_EXPORT ContentSerializedNavigationDriver
   // callers should use SerializedNavigationDriver::Get() instead.
   static ContentSerializedNavigationDriver* GetInstance();
 
+  // Allows an embedder to override the instance returned by GetInstance().
+  static void SetInstance(ContentSerializedNavigationDriver* instance);
+
   // SerializedNavigationDriver implementation.
   int GetDefaultReferrerPolicy() const override;
   bool MapReferrerPolicyToOldValues(int referrer_policy,
@@ -58,12 +60,13 @@ class SESSIONS_EXPORT ContentSerializedNavigationDriver
   // Returns all the registered handlers to deal with the extended info.
   const ExtendedInfoHandlerMap& GetAllExtendedInfoHandlers() const;
 
+ protected:
+  ContentSerializedNavigationDriver();
+
  private:
   friend struct base::DefaultSingletonTraits<ContentSerializedNavigationDriver>;
   friend class ContentSerializedNavigationBuilderTest;
 
-  ContentSerializedNavigationDriver();
-
   ExtendedInfoHandlerMap extended_info_handler_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSerializedNavigationDriver);