Make implicit things explicit when loading scripts.

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index fc9046942654246cd33e0bd4816867ac5d229c4c..41fbb0add6cd4e369aad85acfa3f97eddce16113 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -383,13 +383,17 @@ Dart_Handle DartUtils::ReadStringFromFile(const char* filename) {
 }
 
 
+Dart_Handle DartUtils::SetWorkingDirectory(Dart_Handle builtin_lib) {
+  Dart_Handle directory = NewString(original_working_directory);
+  return SingleArgDart_Invoke(directory, builtin_lib, "_setWorkingDirectory");
+}
+
+
 Dart_Handle DartUtils::ResolveScriptUri(Dart_Handle script_uri,
                                         Dart_Handle builtin_lib) {
-  const int kNumArgs = 3;
+  const int kNumArgs = 1;
   Dart_Handle dart_args[kNumArgs];
-  dart_args[0] = NewString(original_working_directory);
-  dart_args[1] = script_uri;
-  dart_args[2] = (IsWindowsHost() ? Dart_True() : Dart_False());
+  dart_args[0] = script_uri;
   return Dart_Invoke(builtin_lib,
                      NewString("_resolveScriptUri"),
                      kNumArgs,
@@ -399,10 +403,9 @@ Dart_Handle DartUtils::ResolveScriptUri(Dart_Handle script_uri,
 
 Dart_Handle DartUtils::FilePathFromUri(Dart_Handle script_uri,
                                        Dart_Handle builtin_lib) {
-  const int kNumArgs = 2;
+  const int kNumArgs = 1;
   Dart_Handle dart_args[kNumArgs];
   dart_args[0] = script_uri;
-  dart_args[1] = (IsWindowsHost() ? Dart_True() : Dart_False());
   return Dart_Invoke(builtin_lib,
                      NewString("_filePathFromUri"),
                      kNumArgs,
@@ -563,9 +566,6 @@ Dart_Handle DartUtils::LoadScriptHttp(Dart_Handle uri,
 
 Dart_Handle DartUtils::LoadScript(const char* script_uri,
                                   Dart_Handle builtin_lib) {
-  // Always call ResolveScriptUri because as a side effect it sets
-  // the script entry path which is used when automatically resolving
-  // package root.
   Dart_Handle resolved_script_uri =
       ResolveScriptUri(NewString(script_uri), builtin_lib);
   if (Dart_IsError(resolved_script_uri)) {
@@ -665,6 +665,19 @@ Dart_Handle DartUtils::PrepareForScriptLoading(const char* package_root,
   DART_CHECK_VALID(Dart_Invoke(
       async_lib, NewString("_setTimerFactoryClosure"), 1, args));
 
+
+  // Set running on Windows flag.
+  result = Dart_SetField(builtin_lib, NewString("_isWindows"),
+                         (IsWindowsHost() ? Dart_True() : Dart_False()));
+  if (Dart_IsError(result)) {
+    return result;
+  }
+  // Set current working directory.
+  result = SetWorkingDirectory(builtin_lib);
+  if (Dart_IsError(result)) {
+    return result;
+  }
+
   // Set up package root if specified.
   if (package_root != NULL) {
     result = NewString(package_root);