Support displaying of types in the observatory (back-end only for now):

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
===================================================================
--- runtime/vm/isolate.cc	(revision 33387)
+++ runtime/vm/isolate.cc	(working copy)
@@ -753,6 +753,24 @@
     StackZone stack_zone(this);
     HandleScope handle_scope(this);
 
+    // TODO(regis): Remove this debug/coverage code before submitting.
+    {
+      ObjectStore* store = object_store();
+      if (store != NULL) {
+        const Array& table = Array::Handle(store->canonical_type_arguments());
+        ASSERT(table.Length() > 0);
+        TypeArguments& type_args = TypeArguments::Handle();
+        const intptr_t table_size = table.Length() - 1;
+        JSONStream js;
+        for (intptr_t i = 0; i < table_size; i++) {
+          type_args ^= table.At(i);
+          if (!type_args.IsNull()) {
+            type_args.PrintToJSONStream(&js, false);
+          }
+        }
+      }
+    }
+
     // Clean up debugger resources.
     debugger()->Shutdown();
 
@@ -913,6 +931,13 @@
   jsobj.AddProperty("rootLib", lib);
 
   timer_list().PrintTimersToJSONProperty(&jsobj);
+
+  jsobj.AddPropertyF("canonicalTypeArguments", "isolates/%" Pd "/typearguments",

[Ivan Posva, 2014/03/11 08:02:32]

Is this ("isolates/%" Pd "/...", main_port()) really the best way to express ids
within the current isolate()?

[Cutch, 2014/03/11 13:50:01]

It's not necessary (and a bug) to include the isolate ID in an object's ID. 
Also, you should send this as a proper reference (which requires a type and an
id field). e.g:

{
  JSONObject obj(&jsobj, "canonicalTypeArguments");
  typeargRef.AddProperty("type", "@TypeList");
  typeargRef.AddProperty("id", "typearguments");
}

[regis, 2014/03/14 23:52:07]

Done.

+                     static_cast<intptr_t>(main_port()));
+
+  jsobj.AddPropertyF("canonicalTypeArgumentsWithCachedInstantiations",

[Cutch, 2014/03/11 13:50:01]

Same here.

[regis, 2014/03/14 23:52:07]

Done.

+                     "isolates/%" Pd "/typeargumentswithinstantiations",
+                     static_cast<intptr_t>(main_port()));
 }