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

chromeos/ime/composition_text_unittest.cc

Index: chromeos/ime/composition_text_unittest.cc
diff --git a/chromeos/ime/composition_text_unittest.cc b/chromeos/ime/composition_text_unittest.cc
index 0dbe6cd017bbe46e60aff34bb21a639922bbb90f..68f034291911afb9417d2270b0a55d0aa0fcf30b 100644
--- a/chromeos/ime/composition_text_unittest.cc
+++ b/chromeos/ime/composition_text_unittest.cc
@@ -5,12 +5,13 @@
 
 #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};