Support Dart core libraries in source maps.

sdk/lib/_internal/pub/lib/src/sdk.dart

Index: sdk/lib/_internal/pub/lib/src/sdk.dart
diff --git a/sdk/lib/_internal/pub/lib/src/sdk.dart b/sdk/lib/_internal/pub/lib/src/sdk.dart
index bd8314b2062d891a77dd073c687324f759cabd43..a97df46a4bdd4f234c813bd9ab2e35c1f441c741 100644
--- a/sdk/lib/_internal/pub/lib/src/sdk.dart
+++ b/sdk/lib/_internal/pub/lib/src/sdk.dart
@@ -13,10 +13,17 @@ import 'io.dart';
 import 'version.dart';
 
 /// Gets the path to the root directory of the SDK.
-String get rootDirectory {
-  // Assume the Dart executable is always coming from the SDK.
-  return path.dirname(path.dirname(Platform.executable));
-}
+///
+/// When running from the actual built SDK, this will be the SDK that contains
+/// the running Dart executable. When running from the repo, it will be the
+/// "sdk" directory in the Dart repository itself.
+String get rootDirectory =>
+    runningFromSdk ? _rootDirectory : path.join(repoRoot, "sdk");
+
+/// Gets the path to the root directory of the SDK, assuming that the currently
+/// running Dart executable is within it.
+String get _rootDirectory =>
+    path.dirname(path.dirname(Platform.executable));
 
 /// The SDK's revision number formatted to be a semantic version.
 ///
@@ -33,7 +40,7 @@ Version _getVersion() {
   if (sdkVersion != null) return new Version.parse(sdkVersion);
 
   // Read the "version" file.
-  var revisionPath = path.join(rootDirectory, "version");
+  var revisionPath = path.join(_rootDirectory, "version");
   var version = readTextFile(revisionPath).trim();
   return new Version.parse(version);
 }