Refactor the dart api a bit:

runtime/bin/process.cc

Index: runtime/bin/process.cc
===================================================================
--- runtime/bin/process.cc	(revision 651)
+++ runtime/bin/process.cc	(working copy)
@@ -18,14 +18,13 @@
       DartUtils::GetStringValue(Dart_GetNativeArgument(args, 1));
   Dart_Handle arguments = Dart_GetNativeArgument(args, 2);
   ASSERT(Dart_IsArray(arguments));
-  Dart_Result result = Dart_GetLength(arguments);
-  ASSERT(Dart_IsValidResult(result));
-  intptr_t length = Dart_GetResultAsCIntptr(result);
+  intptr_t length = 0;
+  Dart_Handle result = Dart_GetLength(arguments, &length);
+  ASSERT(Dart_IsValid(result));
   char** string_args = new char*[length];
   for (int i = 0; i < length; i++) {
-    result = Dart_ArrayGetAt(arguments, i);
-    ASSERT(Dart_IsValidResult(result));
-    Dart_Handle arg = Dart_GetResult(result);
+    Dart_Handle arg = Dart_ArrayGetAt(arguments, i);
+    ASSERT(Dart_IsValid(arg));
     string_args[i] = const_cast<char *>(DartUtils::GetStringValue(arg));
   }
   Dart_Handle in_handle = Dart_GetNativeArgument(args, 3);