Add explicit base namespace to string16 users.

chrome/common/metrics/variations/experiment_labels_win.h

Index: chrome/common/metrics/variations/experiment_labels_win.h
diff --git a/chrome/common/metrics/variations/experiment_labels_win.h b/chrome/common/metrics/variations/experiment_labels_win.h
index 1c6ae3945510800c6ea6246b1cfa253711fab81d..5df9e5a82b6ad2807b0885cf046f6621b691a576 100644
--- a/chrome/common/metrics/variations/experiment_labels_win.h
+++ b/chrome/common/metrics/variations/experiment_labels_win.h
@@ -13,20 +13,20 @@ namespace chrome_variations {
 // Takes the list of active groups and builds the label for the ones that have
 // Google Update VariationID associated with them. This will return an empty
 // string if there are no such groups.
-string16 BuildGoogleUpdateExperimentLabel(
+base::string16 BuildGoogleUpdateExperimentLabel(
     const base::FieldTrial::ActiveGroups& active_groups);
 
 // Creates a final combined experiment labels string with |variation_labels|
 // and |other_labels|, appropriately appending a separator based on their
 // contents. It is assumed that |variation_labels| and |other_labels| do not
 // have leading or trailing separators.
-string16 CombineExperimentLabels(const string16& variation_labels,
-                                 const string16& other_labels);
+base::string16 CombineExperimentLabels(const base::string16& variation_labels,
+                                       const base::string16& other_labels);
 
 // Takes the value of experiment_labels from the registry and returns a valid
 // experiment_labels string value containing only the labels that are not
 // associated with Chrome Variations.
-string16 ExtractNonVariationLabels(const string16& labels);
+base::string16 ExtractNonVariationLabels(const base::string16& labels);
 
 }  // namespace chrome_variations