Ignore pause on debugger statement when breakpoints are disabled

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 "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2198 matching lines @@
       Handle<Object>(debug_context()->global_proxy(), isolate_),
       arraysize(argv),
       argv);
 }
 
 
 void Debug::HandleDebugBreak() {
   // Ignore debug break during bootstrapping.
   if (isolate_->bootstrapper()->IsActive()) return;
   // Just continue if breaks are disabled.
-  if (break_disabled()) return;
+  if (break_disabled() ||
+      (!break_points_active_ && thread_local_.last_step_action_ == StepNone))

[Yang, 2016/02/12 05:56:23]

Why do we need to check last_step_action_? Stepping in V8 does not go this code
path. I think DevTools does for async stepping, as it uses debug break
interrupts to break asap when it executes in V8? Leaking that implementation
detail over to V8 sounds like a bad choice. And there is no test case for that
in V8.

Since this is only related to the debugger statement, could we simply do the
check for break_points_active_ in Runtime_HandleDebuggerStatement?

[kozy, 2016/02/12 17:22:04]

Hm ,thank you for explanation. I thought that this check will help me to don't
change behavior on paused. I'm going to review devtools async stepping
implementation.

For this patch - yes, we could. Moved check.

+    return;
   // 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()) {
@@ skipping 339 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8