Prefer Dart_SetReturnValue over Dart_PropagateError when it makes sense.

runtime/bin/stdio.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/utils.h"
 #include "bin/stdio.h"
 
 #include "platform/globals.h"
@@ skipping 29 matching lines @@
 
 void FUNCTION_NAME(Stdin_SetLineMode)(Dart_NativeArguments args) {
   bool enabled = DartUtils::GetBooleanValue(Dart_GetNativeArgument(args, 0));
   Stdin::SetLineMode(enabled);
 }
 
 
 void FUNCTION_NAME(Stdout_GetTerminalSize)(Dart_NativeArguments args) {
   if (!Dart_IsInteger(Dart_GetNativeArgument(args, 0))) {
     OSError os_error(-1, "Invalid argument", OSError::kUnknown);
-    Dart_Handle err = DartUtils::NewDartOSError(&os_error);
-    if (Dart_IsError(err)) Dart_PropagateError(err);
-    Dart_SetReturnValue(args, err);
+    Dart_SetReturnValue(args, DartUtils::NewDartOSError(&os_error));
     return;
   }
   intptr_t fd = DartUtils::GetIntptrValue(Dart_GetNativeArgument(args, 0));
   if (fd != 1 && fd != 2) {
-    Dart_PropagateError(Dart_NewApiError("Terminal fd must be 1 or 2"));
+    Dart_SetReturnValue(args, Dart_NewApiError("Terminal fd must be 1 or 2"));
+    return;
   }
 
   int size[2];
   if (Stdout::GetTerminalSize(fd, size)) {
     Dart_Handle list = Dart_NewList(2);
     Dart_ListSetAt(list, 0, Dart_NewInteger(size[0]));
     Dart_ListSetAt(list, 1, Dart_NewInteger(size[1]));
     Dart_SetReturnValue(args, list);
   } else {
     Dart_SetReturnValue(args, DartUtils::NewDartOSError());
   }
 }
 
 }  // namespace bin
 }  // namespace dart