Split the JSON output into multiple lines.

pkg/compiler/lib/src/diagnostics/messages.dart

Index: pkg/compiler/lib/src/diagnostics/messages.dart
diff --git a/pkg/compiler/lib/src/diagnostics/messages.dart b/pkg/compiler/lib/src/diagnostics/messages.dart
index d3dc5815ccd7511de615d330b788f089fac24d8a..84e9cc2a5b166b316d83dc431dda88db56f55db2 100644
--- a/pkg/compiler/lib/src/diagnostics/messages.dart
+++ b/pkg/compiler/lib/src/diagnostics/messages.dart
@@ -428,7 +428,7 @@ enum MessageKind {
   THIS_IS_THE_METHOD,
   THIS_IS_THE_PART_OF_TAG,
   THIS_PROPERTY,
-  THROW_WITHOUT_EXPRESSION,
+  RETHROW_OUTSIDE_CATCH,
   TOP_LEVEL_VARIABLE_DECLARED_STATIC,
   TYPE_ARGUMENT_COUNT_MISMATCH,
   TYPE_VARIABLE_IN_CONSTANT,
@@ -453,7 +453,7 @@ enum MessageKind {
   UNSUPPORTED_EQ_EQ_EQ,
   UNSUPPORTED_LITERAL_SYMBOL,
   UNSUPPORTED_PREFIX_PLUS,
-  UNSUPPORTED_THROW_WITHOUT_EXP,
+  MISSING_EXPRESSION_IN_THROW,
   UNTERMINATED_COMMENT,
   UNTERMINATED_STRING,
   UNTERMINATED_TOKEN,
@@ -1149,11 +1149,6 @@ main() => new C(0);"""]),
         const MessageTemplate(MessageKind.OPTIONAL_PARAMETER_IN_CATCH,
           "Cannot use optional parameters in catch."),
 
-      MessageKind.THROW_WITHOUT_EXPRESSION:
-        const MessageTemplate(MessageKind.THROW_WITHOUT_EXPRESSION,
-          "Cannot use re-throw outside of catch block "
-          "(expression expected after 'throw')."),
-
       MessageKind.UNBOUND_LABEL:
         const MessageTemplate(MessageKind.UNBOUND_LABEL,
           "Cannot resolve label '#{labelName}'."),
@@ -2397,11 +2392,6 @@ main() => A.A = 1;
               "main() => +2;  // No longer a valid way to write '2'"
           ]),
 
-      MessageKind.UNSUPPORTED_THROW_WITHOUT_EXP:
-        const MessageTemplate(MessageKind.UNSUPPORTED_THROW_WITHOUT_EXP,
-          "No expression after 'throw'. "
-          "Did you mean 'rethrow'?"),
-
       MessageKind.DEPRECATED_TYPEDEF_MIXIN_SYNTAX:
         const MessageTemplate(MessageKind.DEPRECATED_TYPEDEF_MIXIN_SYNTAX,
           "'typedef' not allowed here. ",