Add access to the isolate package-root/package-map in Platform.

runtime/bin/platform.cc

Index: runtime/bin/platform.cc
diff --git a/runtime/bin/platform.cc b/runtime/bin/platform.cc
index 0ed2bd364fd10eec6d347472f6233379e94a3cc1..735bc432476664c60001c4656fb8c0b3a378f1f1 100644
--- a/runtime/bin/platform.cc
+++ b/runtime/bin/platform.cc
@@ -85,6 +85,22 @@ void FUNCTION_NAME(Platform_PackageRoot)(Dart_NativeArguments args) {
 }
 
 
+void FUNCTION_NAME(Platform_PackageResolution)(Dart_NativeArguments args) {

[Ivan Posva, 2015/08/26 04:29:35]

There should be no need to rely on C++ code for this feature.

[Lasse Reichstein Nielsen, 2015/08/26 06:26:06]

Excellent. It did seem a bit overengineered to go through C++ to access a Dart
feature.

+  Dart_Handle builtin_lib =
+      Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
+  ASSERT(!Dart_IsError(builtin_lib));
+  Dart_Handle field_name = DartUtils::NewString("_packageRoot");
+  Dart_Handle result = Dart_GetField(builtin_lib, field_name);
+  ASSERT(!Dart_IsError(result));
+  if (Dart_IsNull(result)) {
+    field_name = DartUtils::NewString("_packageMap");
+    result = Dart_GetField(builtin_lib, field_name);
+    ASSERT(!Dart_IsError(result));
+  }
+  Dart_SetReturnValue(args, result);
+}
+
+
 void FUNCTION_NAME(Platform_Environment)(Dart_NativeArguments args) {
   intptr_t count = 0;
   char** env = Platform::Environment(&count);