Replace more ObserverList with base::ObserverList.

ppapi/proxy/ppapi_proxy_test.cc

Index: ppapi/proxy/ppapi_proxy_test.cc
diff --git a/ppapi/proxy/ppapi_proxy_test.cc b/ppapi/proxy/ppapi_proxy_test.cc
index 2b0667c6dbbee332408df8ec354cbcd42c208256..825cf7c340e44cbe149e8ee97f98db58d057cbd9 100644
--- a/ppapi/proxy/ppapi_proxy_test.cc
+++ b/ppapi/proxy/ppapi_proxy_test.cc
@@ -62,10 +62,11 @@ PPB_Proxy_Private ppb_proxy_private = {
 // for the PluginProxyTestHarness and should only respond for PPP interfaces,
 // and the other handler is for the HostProxyTestHarness which should only
 // ever respond for PPB interfaces.
-ObserverList<ProxyTestHarnessBase> get_interface_handlers_;
+base::ObserverList<ProxyTestHarnessBase> get_interface_handlers_;
 
 const void* MockGetInterface(const char* name) {
-  ObserverList<ProxyTestHarnessBase>::Iterator it(&get_interface_handlers_);
+  base::ObserverList<ProxyTestHarnessBase>::Iterator it(
+      &get_interface_handlers_);
   while (ProxyTestHarnessBase* observer = it.GetNext()) {
     const void* interface = observer->GetInterface(name);
     if (interface)