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

runtime/bin/platform.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/platform.h"
 
 #include "include/dart_api.h"
 
 #include "bin/file.h"
 #include "bin/utils.h"
@@ skipping 67 matching lines @@
 
 void FUNCTION_NAME(Platform_PackageRoot)(Dart_NativeArguments args) {
   const char* package_root = Platform::GetPackageRoot();
   if (package_root == NULL) {
     package_root = "";
   }
   Dart_SetReturnValue(args, Dart_NewStringFromCString(package_root));
 }
 
 
+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);
   if (env == NULL) {
     OSError error(-1,
                   "Failed to retrieve environment variables.",
                   OSError::kUnknown);
     Dart_SetReturnValue(args, DartUtils::NewDartOSError(&error));
   } else {
     Dart_Handle result = Dart_NewList(count);
@@ skipping 18 matching lines @@
   }
 }
 
 
 void FUNCTION_NAME(Platform_GetVersion)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, Dart_NewStringFromCString(Dart_VersionString()));
 }
 
 }  // namespace bin
 }  // namespace dart