Revert "Simplify debugger state."

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index 80e6970e34caccbceb0d0f499443b9b6f7bd1dc2..35b29c0d22c6d1d0f84af9724bc7c28086b16f33 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -490,6 +490,7 @@ class Debug {
 
  private:
   explicit Debug(Isolate* isolate);
+  ~Debug();
 
   static bool CompileDebuggerScript(Isolate* isolate, int index);
   void ClearOneShot();
@@ -742,6 +743,25 @@ class LockingCommandMessageQueue BASE_EMBEDDED {
 
 class Debugger {
  public:
+  ~Debugger();
+
+  void DebugRequest(const uint16_t* json_request, int length);
+
+  MUST_USE_RESULT MaybeHandle<Object> MakeJSObject(
+      Vector<const char> constructor_name,
+      int argc,
+      Handle<Object> argv[]);
+  MUST_USE_RESULT MaybeHandle<Object> MakeExecutionState();
+  MUST_USE_RESULT MaybeHandle<Object> MakeBreakEvent(
+      Handle<Object> break_points_hit);
+  MUST_USE_RESULT MaybeHandle<Object> MakeExceptionEvent(
+      Handle<Object> exception,
+      bool uncaught,
+      Handle<Object> promise);
+  MUST_USE_RESULT MaybeHandle<Object> MakeCompileEvent(
+      Handle<Script> script, bool before);
+  MUST_USE_RESULT MaybeHandle<Object> MakeScriptCollectedEvent(int id);
+
   void OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue);
   void OnException(Handle<Object> exception, bool uncaught);
   void OnBeforeCompile(Handle<Script> script);
@@ -753,7 +773,13 @@ class Debugger {
   void OnAfterCompile(Handle<Script> script,
                       AfterCompileFlags after_compile_flags);
   void OnScriptCollected(int id);
-
+  void ProcessDebugEvent(v8::DebugEvent event,
+                         Handle<JSObject> event_data,
+                         bool auto_continue);
+  void NotifyMessageHandler(v8::DebugEvent event,
+                            Handle<JSObject> exec_state,
+                            Handle<JSObject> event_data,
+                            bool auto_continue);
   void SetEventListener(Handle<Object> callback, Handle<Object> data);
   void SetMessageHandler(v8::Debug::MessageHandler handler);
 
@@ -772,13 +798,36 @@ class Debugger {
 
   Handle<Context> GetDebugContext();
 
+  // Unload the debugger if possible. Only called when no debugger is currently
+  // active.
+  void UnloadDebugger();
+  friend void ForceUnloadDebugger();  // In test-debug.cc
+
+  inline bool EventActive() {
+    LockGuard<RecursiveMutex> lock_guard(&debugger_access_);
+
+    // Check whether the message handler was been cleared.
+    // TODO(yangguo): handle loading and unloading of the debugger differently.
+    if (debugger_unload_pending_) {
+      if (isolate_->debug()->debugger_entry() == NULL) {
+        UnloadDebugger();
+      }
+    }
+
+    // Currently argument event is not used.
+    return !ignore_debugger_ && is_active_;
+  }
+
   bool ignore_debugger() const { return ignore_debugger_; }
   void set_live_edit_enabled(bool v) { live_edit_enabled_ = v; }
   bool live_edit_enabled() const {
     return FLAG_enable_liveedit && live_edit_enabled_ ;
   }
 
-  bool is_active() { return is_active_; }
+  bool is_active() {
+    LockGuard<RecursiveMutex> lock_guard(&debugger_access_);
+    return is_active_;
+  }
 
   class IgnoreScope {
    public:
@@ -800,22 +849,6 @@ class Debugger {
 
  private:
   explicit Debugger(Isolate* isolate);
-  ~Debugger();
-
-  MUST_USE_RESULT MaybeHandle<Object> MakeJSObject(
-      Vector<const char> constructor_name,
-      int argc,
-      Handle<Object> argv[]);
-  MUST_USE_RESULT MaybeHandle<Object> MakeExecutionState();
-  MUST_USE_RESULT MaybeHandle<Object> MakeBreakEvent(
-      Handle<Object> break_points_hit);
-  MUST_USE_RESULT MaybeHandle<Object> MakeExceptionEvent(
-      Handle<Object> exception,
-      bool uncaught,
-      Handle<Object> promise);
-  MUST_USE_RESULT MaybeHandle<Object> MakeCompileEvent(
-      Handle<Script> script, bool before);
-  MUST_USE_RESULT MaybeHandle<Object> MakeScriptCollectedEvent(int id);
 
   void CallEventCallback(v8::DebugEvent event,
                          Handle<Object> exec_state,
@@ -828,31 +861,18 @@ class Debugger {
   void CallJSEventCallback(v8::DebugEvent event,
                            Handle<Object> exec_state,
                            Handle<Object> event_data);
-  void UpdateState();
-
-  void ProcessDebugEvent(v8::DebugEvent event,
-                         Handle<JSObject> event_data,
-                         bool auto_continue);
-  void NotifyMessageHandler(v8::DebugEvent event,
-                            Handle<JSObject> exec_state,
-                            Handle<JSObject> event_data,
-                            bool auto_continue);
+  void ListenersChanged();
 
   // Invoke the message handler function.
   void InvokeMessageHandler(MessageImpl message);
 
-  inline bool EventActive() {
-    // Check whether the message handler was been cleared.
-    // TODO(yangguo): handle loading and unloading of the debugger differently.
-    // Currently argument event is not used.
-    return !ignore_debugger_ && is_active_;
-  }
-
+  RecursiveMutex debugger_access_;  // Mutex guarding debugger variables.
   Handle<Object> event_listener_;  // Global handle to listener.
   Handle<Object> event_listener_data_;
   bool is_active_;
   bool ignore_debugger_;  // Are we temporarily ignoring the debugger?
   bool live_edit_enabled_;  // Enable LiveEdit.
+  bool never_unload_debugger_;  // Can we unload the debugger?
   v8::Debug::MessageHandler message_handler_;
   bool debugger_unload_pending_;  // Was message handler cleared?
 
@@ -891,7 +911,8 @@ class EnterDebugger BASE_EMBEDDED {
  private:
   Isolate* isolate_;
   EnterDebugger* prev_;  // Previous debugger entry if entered recursively.
-  bool has_js_frames_;  // Were there any JavaScript frames?
+  JavaScriptFrameIterator it_;
+  const bool has_js_frames_;  // Were there any JavaScript frames?
   StackFrame::Id break_frame_id_;  // Previous break frame id.
   int break_id_;  // Previous break id.
   bool load_failed_;  // Did the debugger fail to load?