Switch to static_assert in base/.

base/strings/string16.h

Index: base/strings/string16.h
diff --git a/base/strings/string16.h b/base/strings/string16.h
index 1a01a9613e78dc67685d96a7269cd2569d7e9c2c..ba4ffe788a48ec10470c5417a862aa172e9c6f0a 100644
--- a/base/strings/string16.h
+++ b/base/strings/string16.h
@@ -64,7 +64,8 @@ struct string16_char_traits {
 
   // int_type needs to be able to hold each possible value of char_type, and in
   // addition, the distinct value of eof().
-  COMPILE_ASSERT(sizeof(int_type) > sizeof(char_type), unexpected_type_width);
+  static_assert(sizeof(int_type) > sizeof(char_type),
+                "int must be larger than 16 bits wide");
 
   typedef std::streamoff off_type;
   typedef mbstate_t state_type;