Restoring the chrome variatioons client, with a fix for browser_test failures caused by it.

chrome/test/base/testing_browser_process.cc

Index: chrome/test/base/testing_browser_process.cc
diff --git a/chrome/test/base/testing_browser_process.cc b/chrome/test/base/testing_browser_process.cc
index 37cbc488fe4e9a5f5c05383df2c17f27cba2cf0e..8cb8a7896a2ab88e856114e5f2107029e2c74fa5 100644
--- a/chrome/test/base/testing_browser_process.cc
+++ b/chrome/test/base/testing_browser_process.cc
@@ -62,6 +62,10 @@ PrefService* TestingBrowserProcess::local_state() {
   return local_state_;
 }
 
+VariationsService* TestingBrowserProcess::variations_service() {
+  return NULL;
+}
+
 policy::BrowserPolicyConnector*
     TestingBrowserProcess::browser_policy_connector() {
 #if defined(ENABLE_CONFIGURATION_POLICY)