Add instrumentation data to the analysis server diagnostics page.

pkg/analyzer/lib/instrumentation/instrumentation.dart

Index: pkg/analyzer/lib/instrumentation/instrumentation.dart
diff --git a/pkg/analyzer/lib/instrumentation/instrumentation.dart b/pkg/analyzer/lib/instrumentation/instrumentation.dart
index abc2799315e8927bd90df7a6999f164dedddb0e3..49919fc642a0fbe0b7412452ac9b4d80dac42f37 100644
--- a/pkg/analyzer/lib/instrumentation/instrumentation.dart
+++ b/pkg/analyzer/lib/instrumentation/instrumentation.dart
@@ -28,6 +28,11 @@ abstract class InstrumentationServer {
   String get sessionId;
 
   /**
+   * A user-friendly description of this instrumentation server.
+   */
+  String get describe;
+
+  /**
    * Pass the given [message] to the instrumentation server so that it will be
    * logged with other messages.
    *
@@ -110,6 +115,8 @@ class InstrumentationService {
    */
   String get _timestamp => new DateTime.now().millisecondsSinceEpoch.toString();
 
+  InstrumentationServer get instrumentationServer => _instrumentationServer;
+
   /**
    * Log that the given analysis [task] is being performed in the given
    * [context].
@@ -370,6 +377,13 @@ class MulticastInstrumentationServer implements InstrumentationServer {
   String get sessionId => _servers[0].sessionId;
 
   @override
+  String get describe {
+    return _servers
+        .map((InstrumentationServer server) => server.describe)
+        .join("\n");
+  }
+
+  @override
   void log(String message) {
     for (InstrumentationServer server in _servers) {
       server.log(message);