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

chrome/browser/spellchecker/spellcheck_host_metrics.cc

Index: chrome/browser/spellchecker/spellcheck_host_metrics.cc
diff --git a/chrome/browser/spellchecker/spellcheck_host_metrics.cc b/chrome/browser/spellchecker/spellcheck_host_metrics.cc
index e2cb473c270fc6ac45c4f6cc531ce3efc7974beb..6e4f134bdd233d4a21681a441b0648a9beee6615 100644
--- a/chrome/browser/spellchecker/spellcheck_host_metrics.cc
+++ b/chrome/browser/spellchecker/spellcheck_host_metrics.cc
@@ -60,7 +60,7 @@ void SpellCheckHostMetrics::RecordCheckedWordStats(const base::string16& word,
   // Collects actual number of checked words, excluding duplication.
   base::MD5Digest digest;
   base::MD5Sum(reinterpret_cast<const unsigned char*>(word.c_str()),
-         word.size() * sizeof(char16), &digest);
+         word.size() * sizeof(base::char16), &digest);
   checked_word_hashes_.insert(base::MD5DigestToBase16(digest));
 
   RecordWordCounts();