Expose content shell's remote debugging URL.

lib/src/runner/vm/environment.dart

Index: lib/src/runner/vm/environment.dart
diff --git a/lib/src/runner/vm/environment.dart b/lib/src/runner/vm/environment.dart
index 984d14c17478b05dd2a60f4a8d1a49b3561c10f5..b7480ea9eb75a2e1636214f42fd1bc85ebdc9651 100644
--- a/lib/src/runner/vm/environment.dart
+++ b/lib/src/runner/vm/environment.dart
@@ -14,6 +14,9 @@ class VMEnvironment implements Environment {
   Uri get observatoryUrl => throw new UnsupportedError(
       "VMEnvironment.observatoryUrl is not currently supported.");
 
+  Uri get remoteDebuggerUrl => throw new UnsupportedError(
+      "VMEnvironment.observatoryUrl is not supported.");
+
   CancelableFuture displayPause() =>
       throw new UnsupportedError(
           "The VM doesn't yet support Environment.displayPause.");