Fix causal_async_star_stack_contents_test with optimization-counter-threshold=5

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 1662 matching lines @@
 
   intptr_t synchronous_stack_trace_length =
       StackTraceUtils::CountFrames(thread, 0, async_function);
 
   // Append the top frames from the synchronous stack trace, up until the active
   // asynchronous function. We truncate the remainder of the synchronous
   // stack trace because it contains activations that are part of the
   // asynchronous dispatch mechanisms.
   StackFrameIterator iterator(false);
   StackFrame* frame = iterator.NextFrame();
-  while (synchronous_stack_trace_length >= 0) {
+  while (synchronous_stack_trace_length > 0) {
     ASSERT(frame != NULL);
     if (frame->IsDartFrame()) {
       code = frame->LookupDartCode();
       AppendCodeFrames(thread, isolate, zone, stack_trace, frame, &code,
                        &inlined_code, &deopt_frame);
       synchronous_stack_trace_length--;
     }
     frame = iterator.NextFrame();
   }
 
@@ skipping 2137 matching lines @@
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart