Sync/Valgrind: Add gmock printers for SyncChange, SyncData, SyncError.

chrome/browser/sync/api/sync_change.cc

Index: chrome/browser/sync/api/sync_change.cc
diff --git a/chrome/browser/sync/api/sync_change.cc b/chrome/browser/sync/api/sync_change.cc
index afd321d646d7d31f16541f07ceaf64e0fdf9ac36..1d8e58a5d8da6d11ad128dbe871eef4e81c98171 100644
--- a/chrome/browser/sync/api/sync_change.cc
+++ b/chrome/browser/sync/api/sync_change.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/sync/api/sync_change.h"
 
+#include <ostream>
+
 SyncChange::SyncChange() : change_type_(ACTION_INVALID) {
 }
 
@@ -59,3 +61,12 @@ std::string SyncChange::ChangeTypeToString(SyncChangeType change_type) {
   }
   return std::string();
 }
+
+std::string SyncChange::ToString() const {
+  return "{ changeType: " + ChangeTypeToString(change_type_) +
+      ", syncData: " + sync_data_.ToString() + "}";
+}
+
+void PrintTo(const SyncChange& sync_change, std::ostream* os) {
+  *os << sync_change.ToString();
+}