Use base::string16 for CompositionText.Text instead of converting to utf-8 and back unnecessarily.

chromeos/ime/composition_text_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 // TODO(nona): Add more tests.
 
 #include "chromeos/ime/composition_text.h"
 
+#include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace chromeos {
 
 TEST(CompositionTextTest, CopyTest) {
-  const char kSampleText[] = "Sample Text";
+  const base::string16 kSampleText = base::UTF8ToUTF16("Sample Text");
   const CompositionText::UnderlineAttribute kSampleUnderlineAttribute1 = {
     CompositionText::COMPOSITION_TEXT_UNDERLINE_SINGLE, 10, 20};
 
   const CompositionText::UnderlineAttribute kSampleUnderlineAttribute2 = {
     CompositionText::COMPOSITION_TEXT_UNDERLINE_DOUBLE, 11, 21};
 
   const CompositionText::UnderlineAttribute kSampleUnderlineAttribute3 = {
     CompositionText::COMPOSITION_TEXT_UNDERLINE_ERROR, 12, 22};
 
   // Make CompositionText
@@ skipping 20 matching lines @@
               text2.underline_attributes()[i].start_index);
     EXPECT_EQ(text.underline_attributes()[i].end_index,
               text2.underline_attributes()[i].end_index);
   }
 
   EXPECT_EQ(text.selection_start(), text2.selection_start());
   EXPECT_EQ(text.selection_end(), text2.selection_end());
 }
 
 }  // namespace chromeos