Expose content shell's remote debugging URL.

lib/src/runner/browser/browser_manager.dart

Index: lib/src/runner/browser/browser_manager.dart
diff --git a/lib/src/runner/browser/browser_manager.dart b/lib/src/runner/browser/browser_manager.dart
index 321c1f78c8f88190060a9f8cd3de6bc95b51ba1e..5442d7528d1dfa66af34b93fa60740bf3fac812f 100644
--- a/lib/src/runner/browser/browser_manager.dart
+++ b/lib/src/runner/browser/browser_manager.dart
@@ -151,7 +151,13 @@ class BrowserManager {
   Future<_BrowserEnvironment> _loadBrowserEnvironment() async {
     var observatoryUrl;
     if (_platform.isDartVM) observatoryUrl = await _browser.observatoryUrl;
-    return new _BrowserEnvironment(this, observatoryUrl);
+
+    var remoteDebuggerUrl;
+    if (_platform == TestPlatform.contentShell) {
+      remoteDebuggerUrl = await _browser.remoteDebuggerUrl;
+    }
+
+    return new _BrowserEnvironment(this, observatoryUrl, remoteDebuggerUrl);
   }
 
   /// Tells the browser the load a test suite from the URL [url].
@@ -285,7 +291,10 @@ class _BrowserEnvironment implements Environment {
 
   final Uri observatoryUrl;
 
-  _BrowserEnvironment(this._manager, this.observatoryUrl);
+  final Uri remoteDebuggerUrl;
+
+  _BrowserEnvironment(this._manager, this.observatoryUrl,
+      this.remoteDebuggerUrl);
 
   CancelableFuture displayPause() => _manager._displayPause();
 }