[inspector] ignores debugger; in blackboxed code

src/debug/debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/debug/debug.h"
 
 #include <memory>
 
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 2121 matching lines @@
 
   StackLimitCheck check(isolate_);
   if (check.HasOverflowed()) return;
 
   { JavaScriptFrameIterator it(isolate_);
     DCHECK(!it.done());
     Object* fun = it.frame()->function();
     if (fun && fun->IsJSFunction()) {
       // Don't stop in builtin functions.
       if (!JSFunction::cast(fun)->shared()->IsSubjectToDebugging()) return;
-      if (isolate_->stack_guard()->CheckDebugBreak() &&
-          IsBlackboxed(JSFunction::cast(fun)->shared())) {
+      if (IsBlackboxed(JSFunction::cast(fun)->shared())) {

[Yang, 2017/01/25 06:03:52]

Why do we need to deoptimize the function? We don't do this for regular
optimized functions that have a debugger statement. Simply returning should be
fine imo.

[kozy, 2017/01/25 06:10:44]

I think when we schedule pause on next statement for async break points, we can
enter to this function on function call and we would like to deoptimize this
function if it's blackboxed to correctly break on enter to inner function.
As proof: one of inspector test about async breakpoints are flaky without this
code.

[Yang, 2017/01/25 08:32:34]

As discussed, please also deopt the function for the case of not subject to
debugging. And add a comment for why this is necessary, with a TODO to remove
once we have break-on-entry.

         Deoptimizer::DeoptimizeFunction(JSFunction::cast(fun));
         return;
       }
       JSGlobalObject* global =
           JSFunction::cast(fun)->context()->global_object();
       // Don't stop in debugger functions.
       if (IsDebugGlobal(global)) return;
       // Don't stop if the break location is muted.
       if (IsMutedAtCurrentLocation(it.frame())) return;
     }
@@ skipping 180 matching lines @@
   return v8::Utils::ToLocal(callback_data_);
 }
 
 
 v8::Isolate* EventDetailsImpl::GetIsolate() const {
   return reinterpret_cast<v8::Isolate*>(exec_state_->GetIsolate());
 }
 
 }  // namespace internal
 }  // namespace v8