Update some uses of char16 to use the base:: namespace.

content/common/indexed_db/indexed_db_key_unittest.cc

Index: content/common/indexed_db/indexed_db_key_unittest.cc
diff --git a/content/common/indexed_db/indexed_db_key_unittest.cc b/content/common/indexed_db/indexed_db_key_unittest.cc
index ca52cc4a134684b38b853b8c690f5659e4b62e34..b7eb11d525a93b1d541ba314db380822ed63ab61 100644
--- a/content/common/indexed_db/indexed_db_key_unittest.cc
+++ b/content/common/indexed_db/indexed_db_key_unittest.cc
@@ -32,9 +32,9 @@ TEST(IndexedDBKeyTest, KeySizeEstimates) {
   keys.push_back(IndexedDBKey(date, blink::WebIDBKeyTypeDate));
   estimates.push_back(static_cast<size_t>(24));  // Overhead + sizeof(double).
 
-  const base::string16 string(1024, static_cast<char16>('X'));
+  const base::string16 string(1024, static_cast<base::char16>('X'));
   keys.push_back(IndexedDBKey(string));
-  // Overhead + string length * sizeof(char16).
+  // Overhead + string length * sizeof(base::char16).
   estimates.push_back(static_cast<size_t>(2064));
 
   const size_t array_size = 1024;