Stop doing unnecessary UTF-8 to UTF-16 conversions in JSONWriter.

base/third_party/icu/icu_utf.h

Index: base/third_party/icu/icu_utf.h
diff --git a/base/third_party/icu/icu_utf.h b/base/third_party/icu/icu_utf.h
index 9cb124727326dd88ebf55a12ecb83e256350e2fa..a000816c36208144ce3098ca6ff99b08719a7821 100644
--- a/base/third_party/icu/icu_utf.h
+++ b/base/third_party/icu/icu_utf.h
@@ -22,6 +22,7 @@
 namespace base_icu {
 
 typedef uint32 UChar32;
+typedef uint16 UChar;
 typedef int8 UBool;
 
 // General ---------------------------------------------------------------------
@@ -304,7 +305,7 @@ UChar32 utf8_nextCharSafeBody(const uint8 *s, int32 *pi, int32 length, UChar32 c
  * @return lead surrogate (U+d800..U+dbff) for supplementary
  * @stable ICU 2.4
  */
-#define CBU16_LEAD(supplementary) (UChar)(((supplementary)>>10)+0xd7c0)
+#define CBU16_LEAD(supplementary) (base_icu::UChar)(((supplementary)>>10)+0xd7c0)
 
 /**
  * Get the trail surrogate (0xdc00..0xdfff) for a
@@ -313,7 +314,7 @@ UChar32 utf8_nextCharSafeBody(const uint8 *s, int32 *pi, int32 length, UChar32 c
  * @return trail surrogate (U+dc00..U+dfff) for supplementary
  * @stable ICU 2.4
  */
-#define CBU16_TRAIL(supplementary) (UChar)(((supplementary)&0x3ff)|0xdc00)
+#define CBU16_TRAIL(supplementary) (base_icu::UChar)(((supplementary)&0x3ff)|0xdc00)
 
 /**
  * How many 16-bit code units are used to encode this Unicode code point? (1 or 2)