[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 2119 matching lines @@
   // Ignore debug break if debugger is not active.
   if (!is_active()) return;
 
   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() &&
+      // Don't stop in builtin and blackboxed functions.
+      if (!JSFunction::cast(fun)->shared()->IsSubjectToDebugging() ||
           IsBlackboxed(JSFunction::cast(fun)->shared())) {
+        // Inspector uses pause on next statement for asynchronous breakpoints.
+        // When breakpoint is fired we try to break on first not blackboxed
+        // statement. To achieve this goal we need to deoptimize current
+        // function and don't clear requested DebugBreak even if it's blackboxed
+        // to be able to break on not blackboxed function call.
+        // TODO(yangguo): introduce break_on_function_entry since current
+        // implementation is slow.
         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