Add function for one-time stop at function entry

runtime/bin/main.cc

Index: runtime/bin/main.cc
===================================================================
--- runtime/bin/main.cc	(revision 17321)
+++ runtime/bin/main.cc	(working copy)
@@ -545,9 +545,7 @@
       function_name = DartUtils::NewString(dot + 1);
     }
     free(bpt_function);
-    Dart_Breakpoint bpt;
-    result = Dart_SetBreakpointAtEntry(
-                 library, class_name, function_name, &bpt);
+    result = Dart_OneTimeBreakAtEntry(library, class_name, function_name);
   }
   return result;
 }