Move session_id.{cc,h} from chrome/browser/sessions to components/sessions

components/sessions/session_id.cc

Index: components/sessions/session_id.cc
diff --git a/ui/gfx/display_observer.cc b/components/sessions/session_id.cc
similarity index 57%
copy from ui/gfx/display_observer.cc
copy to components/sessions/session_id.cc
index f8e3c07640164e35c05b76337238ab49eecb59cd..eb65abdd252019f2093e7edf39485ed61c8d6b24 100644
--- a/ui/gfx/display_observer.cc
+++ b/components/sessions/session_id.cc
@@ -2,11 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ui/gfx/display_observer.h"
+#include "components/sessions/session_id.h"
 
-namespace gfx {
+static SessionID::id_type next_id = 1;
 
-DisplayObserver::~DisplayObserver() {
+SessionID::SessionID() {
+  id_ = next_id++;
 }
-
-}  // namespace gfx