[futex] Allow debugger to break in the middle of a futexWait

src/debug/debug.h

Index: src/debug/debug.h
diff --git a/src/debug/debug.h b/src/debug/debug.h
index b499eb0eb89db3dabfedbee1c4539586e3bd0c38..e325257547770655d1104feb213feb90f1ff7c6e 100644
--- a/src/debug/debug.h
+++ b/src/debug/debug.h
@@ -597,6 +597,7 @@ class Debug {
   bool in_debug_event_listener_;
   bool break_on_exception_;
   bool break_on_uncaught_exception_;
+  bool break_in_nondebuggable_;
 
   DebugInfoListNode* debug_info_list_;  // List of active debug info objects.
 
@@ -662,6 +663,7 @@ class Debug {
   friend class DisableBreak;
   friend class LiveEdit;
   friend class SuppressDebug;
+  friend class EnableBreakInNonDebuggable;
 
   friend Handle<FixedArray> GetDebuggedFunctions();  // In test-debug.cc
   friend void CheckDebuggerUnloaded(bool check_functions);  // In test-debug.cc
@@ -720,6 +722,23 @@ class DisableBreak BASE_EMBEDDED {
 };
 
 
+// Stack allocated class for enabling breaking in a normally non-debuggable
+// function (e.g. a builtin).
+class EnableBreakInNonDebuggable BASE_EMBEDDED {
+ public:
+  explicit EnableBreakInNonDebuggable(Debug* debug, bool enable)
+      : debug_(debug), previous_(debug->break_in_nondebuggable_) {
+    debug_->break_in_nondebuggable_ = enable;
+  }
+  ~EnableBreakInNonDebuggable() { debug_->break_in_nondebuggable_ = previous_; }
+
+ private:
+  Debug* debug_;
+  bool previous_;
+  DISALLOW_COPY_AND_ASSIGN(EnableBreakInNonDebuggable);
+};
+
+
 class SuppressDebug BASE_EMBEDDED {
  public:
   explicit SuppressDebug(Debug* debug)