Split dart:builtin into dart:builtin and dart:io.

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index 9266f6a448a3b26a20e2704d7aa002afa4e5812d..962748aec3bda762e6135ae4bf01e66c8c08024e 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -12,7 +12,9 @@ const char* DartUtils::kDartScheme = "dart:";
 const char* DartUtils::kBuiltinLibURL = "dart:builtin";
 const char* DartUtils::kCoreLibURL = "dart:core";
 const char* DartUtils::kCoreImplLibURL = "dart:coreimpl";
-const char* DartUtils::kCoreNativeWrappersLibURL = "dart:nativewrappers";
+const char* DartUtils::kIOLibURL = "dart:io";
+
+
 const char* DartUtils::kIdFieldName = "_id";
 
 
@@ -98,6 +100,12 @@ bool DartUtils::IsDartSchemeURL(const char* url_name) {
 }
 
 
+bool DartUtils::IsDartIOLibURL(const char* url_name) {
+  return (strcmp(url_name, kIOLibURL) == 0);
+}
+
+
+
 Dart_Handle DartUtils::CanonicalizeURL(CommandLineOptions* url_mapping,
                                        Dart_Handle library,
                                        const char* url_str) {