Update some uses of UTF conversions in chrome/browser to use the base:: namespace.

chrome/browser/spellchecker/word_trimmer_unittest.cc

Index: chrome/browser/spellchecker/word_trimmer_unittest.cc
diff --git a/chrome/browser/spellchecker/word_trimmer_unittest.cc b/chrome/browser/spellchecker/word_trimmer_unittest.cc
index 6bea065ebd85ce7d39d058fdfeed701f6fd34120..35b8e6a62298d9795cdca2a338bffc245bb0709e 100644
--- a/chrome/browser/spellchecker/word_trimmer_unittest.cc
+++ b/chrome/browser/spellchecker/word_trimmer_unittest.cc
@@ -7,6 +7,8 @@
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using base::ASCIIToUTF16;
+
 TEST(WordTrimmerTest, TrimWordsEmptyText) {
   size_t start = 0;
   size_t end = 0;