Add debugger functions to inspect objects and classes

runtime/vm/debugger.h

Index: runtime/vm/debugger.h
===================================================================
--- runtime/vm/debugger.h	(revision 3572)
+++ runtime/vm/debugger.h	(working copy)
@@ -144,9 +144,18 @@
   // Called from Runtime when a breakpoint in Dart code is reached.
   void BreakpointCallback();
 
+  RawArray* GetInstanceFields(const Instance& obj);

[siva, 2012/01/26 21:34:08]

I am wondering whether it would make sense to just have

RawArray* GetFields(const Instance& obj);

Which lists all the fields and tags the static fields with a static qualifier.

Also do you think we need to dump the native fields of an object if present?

[hausner, 2012/01/27 17:19:30]

I was envisioning that the static fields of a class would be displayed at a
different place in the debugger, so separating them made sense. Also, how would
you qualify static fields? Adding a third array element per field seems totally
overkill for that.

+  RawArray* GetStaticFields(const Class& cls);
+
   // Utility functions.
   static const char* QualifiedFunctionName(const Function& func);
 
+  RawInstance* GetInstanceField(const Class& cls,
+                                const String& field_name,
+                                const Instance& object);
+  RawInstance* GetStaticField(const Class& cls,
+                              const String& field_name);

[siva, 2012/01/26 21:34:08]

There is a certain amount of overlap between these functions and the ones in
dart_api_impl.cc
Dart_GetInstanceField
Dart_GetStaticField
Maybe we should move your implementation to dart_entry.h and use it both from
here and the dart_api functions.

[hausner, 2012/01/27 17:19:30]

I looked at that code when I implemented this. The difference is that the code
in dart_api_impl does a lookup whether the field actually exists, whereas these
functions require that the field exists (the lookup is done by the caller).
Also, I didn't want to deal with setters.

I did see that the dart_api_impl code is out of date (does not use some of the
getter lookup code you recently added) so I'll add a todo that long-term we
should refactor this code.

+
  private:
   Breakpoint* SetBreakpoint(const Function& target_function,
                             intptr_t token_index);