Fix a couple of bugs with async stack traces

runtime/vm/debugger.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/debugger.h"
 
 #include "include/dart_api.h"
 
 #include "platform/address_sanitizer.h"
 
@@ skipping 669 matching lines @@
     // TODO(hausner): What to do if there is no descriptor entry
     // for the code position of the frame? For now say we are at context
     // level 0.
     TokenPos();
     if (token_pos_ == TokenPosition::kNoSource) {
       // No PcDescriptor.
       return context_level_;
     }
     ASSERT(!pc_desc_.IsNull());
     TokenPosition innermost_begin_pos = TokenPosition::kMinSource;
-    TokenPosition activation_token_pos = TokenPos();
+    TokenPosition activation_token_pos = TokenPos().FromSynthetic();
     ASSERT(activation_token_pos.IsReal());
     GetVarDescriptors();
     intptr_t var_desc_len = var_descriptors_.Length();
     for (intptr_t cur_idx = 0; cur_idx < var_desc_len; cur_idx++) {
       RawLocalVarDescriptors::VarInfo var_info;
       var_descriptors_.GetInfo(cur_idx, &var_info);
       const int8_t kind = var_info.kind();
       if ((kind == RawLocalVarDescriptors::kContextLevel) &&
           (var_info.begin_pos <= activation_token_pos) &&
           (activation_token_pos < var_info.end_pos)) {
@@ skipping 50 matching lines @@
 RawObject* ActivationFrame::GetAsyncCompleterAwaiter(const Object& completer) {
   const Class& sync_completer_cls = Class::Handle(completer.clazz());
   ASSERT(!sync_completer_cls.IsNull());
   const Class& completer_cls = Class::Handle(sync_completer_cls.SuperClass());
   const Field& future_field =
       Field::Handle(completer_cls.LookupInstanceFieldAllowPrivate(
           Symbols::CompleterFuture()));
   ASSERT(!future_field.IsNull());
   Instance& future = Instance::Handle();
   future ^= Instance::Cast(completer).GetField(future_field);
-  ASSERT(!future.IsNull());
+  if (future.IsNull()) {
+    // The completer object may not be fully initialized yet.
+    return Object::null();
+  }
   const Class& future_cls = Class::Handle(future.clazz());
   ASSERT(!future_cls.IsNull());
   const Field& awaiter_field = Field::Handle(
       future_cls.LookupInstanceFieldAllowPrivate(Symbols::_Awaiter()));
   ASSERT(!awaiter_field.IsNull());
   return future.GetField(awaiter_field);
 }
 
 
 RawObject* ActivationFrame::GetAsyncStreamControllerStream() {
@@ skipping 652 matching lines @@
 
 
 void DebuggerStackTrace::AddActivation(ActivationFrame* frame) {
   if (IsFunctionVisible(frame->function())) {
     trace_.Add(frame);
   }
 }
 
 
 void DebuggerStackTrace::AddMarker(ActivationFrame::Kind marker) {
-  ASSERT((marker >= ActivationFrame::kAsyncSuspensionMarker) &&
-         (marker <= ActivationFrame::kAsyncSuspensionMarker));
+  ASSERT(marker == ActivationFrame::kAsyncSuspensionMarker);
   trace_.Add(new ActivationFrame(marker));
 }
 
 
 void DebuggerStackTrace::AddAsyncCausalFrame(uword pc, const Code& code) {
   trace_.Add(new ActivationFrame(pc, 0, 0, code, Array::Handle(), 0,
                                  ActivationFrame::kAsyncCausal));
 }
 
 
@@ skipping 2823 matching lines @@
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart