Improve class-tree, class-view, and instance-view.

runtime/vm/service/service.md

 # Dart VM Service Protocol 3.3
 
 > Please post feedback to the [observatory-discuss group][discuss-list]
 
 This document describes of _version 3.3_ of the Dart VM Service Protocol. This
 protocol is used to communicate with a running Dart Virtual Machine.
 
 To use the Service Protocol, start the VM with the *--observe* flag.
 The VM will start a webserver which services protocol requests via WebSocket.
 It is possible to make HTTP (non-WebSocket) requests,
@@ skipping 953 matching lines @@
 
   // The library which contains this class.
   @Library library;
 
   // The location of this class in the source code.
   SourceLocation location [optional];
 
   // The superclass of this class, if any.
   @Class super [optional];
 
+  // The supertype for this class, if any.
+  //
+  // The value will be of the kind: Type.
+  @Instance superType [optional];
+
   // A list of interface types for this class.
   //
+  // The values will be of the kind: Type.
+  @Instance[] interfaces;
+
+  // The mixin type for this class, if any.
+  //
   // The value will be of the kind: Type.
-  @Instance[] interfaces;
+  @Instance mixin [optional];
 
   // A list of fields in this class. Does not include fields from
   // superclasses.
   @Field[] fields;
 
   // A list of functions in this class. Does not include functions
   // from superclasses.
   @Function[] functions;
 
   // A list of subclasses of this class.
@@ skipping 1513 matching lines @@
 ## Revision History
 
 version | comments
 ------- | --------
 1.0 | initial revision
 2.0 | Describe protocol version 2.0.
 3.0 | Describe protocol version 3.0.  Added UnresolvedSourceLocation.  Added Sentinel return to getIsolate.  Add AddedBreakpointWithScriptUri.  Removed Isolate.entry. The type of VM.pid was changed from string to int.  Added VMUpdate events.  Add offset and count parameters to getObject() and offset and count fields to Instance. Added ServiceExtensionAdded event.
 3.1 | Add the getSourceReport RPC.  The getObject RPC now accepts offset and count for string objects.  String objects now contain length, offset, and count properties.
 3.2 | Isolate objects now include the runnable bit and many debugger related RPCs will return an error if executed on an isolate before it is runnable.
 3.3 | Pause event now indicates if the isolate is paused at an await, yield, or yield* suspension point via the 'atAsyncSuspension' field. Resume command now supports the step parameter 'OverAsyncSuspension'. A Breakpoint added synthetically by an 'OverAsyncSuspension' resume command identifies itself as such via the 'isSyntheticAsyncContinuation' field.
-
+3.4 | Add the superType and mixin fields to Class.
 [discuss-list]: https://groups.google.com/a/dartlang.org/forum/#!forum/observatory-discuss