Add kInvalidExceptionPauseInfo and fix the build

runtime/vm/service.cc

Index: runtime/vm/service.cc
diff --git a/runtime/vm/service.cc b/runtime/vm/service.cc
index a0f7f1b91fea8b326b44e71c57be036aba6584ae..4662ff9fdd0a1a90e602fc52a4ab9578b5f16ec1 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -3019,7 +3019,7 @@ static Dart_ExceptionPauseInfo exception_pause_mode_values[] = {
   kPauseOnAllExceptions,
   kNoPauseOnExceptions,
   kPauseOnUnhandledExceptions,
-  static_cast<Dart_ExceptionPauseInfo>(-1),  // Fall through.
+  kInvalidExceptionPauseInfo,
 };
 
 
@@ -3038,7 +3038,7 @@ static bool SetExceptionPauseMode(Isolate* isolate, JSONStream* js) {
   }
   Dart_ExceptionPauseInfo info =
       EnumMapper(mode, exception_pause_mode_names, exception_pause_mode_values);
-  if (info == -1) {
+  if (info == kInvalidExceptionPauseInfo) {
     PrintInvalidParamError(js, "mode");
     return true;
   }