GCAPI should append to the existing experiment_labels instead of clobbering them.

chrome/installer/util/google_update_experiment_util.h

Index: chrome/installer/util/google_update_experiment_util.h
diff --git a/chrome/installer/util/google_update_experiment_util.h b/chrome/installer/util/google_update_experiment_util.h
index 33d542f3209c66ccd18fac21d18fcee0e493631a..b9898b32f45770c3e35efa0a8780fdcfbb34290c 100644
--- a/chrome/installer/util/google_update_experiment_util.h
+++ b/chrome/installer/util/google_update_experiment_util.h
@@ -7,11 +7,15 @@
 
 #include "base/strings/string16.h"
 
+namespace base {
+class Time;
+}
+
 namespace installer {
 
 // Constructs a date string in the format understood by Google Update for the
-// current time plus one year.
-string16 BuildExperimentDateString();
+// |current_time| plus one year.
+string16 BuildExperimentDateString(const base::Time& current_time);
 
 }  // namespace installer