Expose the exceptions info in the diagnostics page.

pkg/analysis_server/lib/src/status/pages.dart

Index: pkg/analysis_server/lib/src/status/pages.dart
diff --git a/pkg/analysis_server/lib/src/status/pages.dart b/pkg/analysis_server/lib/src/status/pages.dart
index 096032f23923cc01369775e114f2099cbc5ba982..ae6f898e5c77a017fce5798c09758d899f8a84cd 100644
--- a/pkg/analysis_server/lib/src/status/pages.dart
+++ b/pkg/analysis_server/lib/src/status/pages.dart
@@ -149,6 +149,16 @@ abstract class Page {
     }
   }
 
+  void pre(void gen(), {String classes}) {
+    if (classes != null) {
+      buf.write('<pre class="$classes">');
+    } else {
+      buf.write('<pre>');
+    }
+    gen();
+    buf.writeln('</pre>');
+  }
+
   void blankslate(String str) {
     div(() => buf.writeln(str), classes: 'blankslate');
   }