Support LiveEdit when standing on return operator

Review URL: http://codereview.chromium.org/6894014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7708 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/debug.cc

@@ -989,6 +989,11 @@ Object* Debug::Break(Arguments args) {
   } else if (thread_local_.frame_drop_mode_ ==
       FRAME_DROPPED_IN_DIRECT_CALL) {
     // Nothing to do, after_break_target is not used here.
+  } else if (thread_local_.frame_drop_mode_ ==
+      FRAME_DROPPED_IN_RETURN_CALL) {
+    Code* plain_return = isolate_->builtins()->builtin(
+        Builtins::kFrameDropper_LiveEdit);
+    thread_local_.after_break_target_ = plain_return->entry();
   } else {
     UNREACHABLE();
   }

src/debug.h

@@ -422,7 +422,8 @@ class Debug {
     FRAME_DROPPED_IN_DEBUG_SLOT_CALL,
     // The top JS frame had been calling some C++ function. The return address
     // gets patched automatically.
-    FRAME_DROPPED_IN_DIRECT_CALL
+    FRAME_DROPPED_IN_DIRECT_CALL,
+    FRAME_DROPPED_IN_RETURN_CALL
   };
 
   void FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,

src/liveedit.cc

@@ -1411,6 +1411,9 @@ static const char* DropFrames(Vector<StackFrame*> frames,
           Builtins::kFrameDropper_LiveEdit)) {
     // OK, we can drop our own code.
     *mode = Debug::FRAME_DROPPED_IN_DIRECT_CALL;
+  } else if (pre_top_frame_code ==
+      isolate->builtins()->builtin(Builtins::kReturn_DebugBreak)) {
+    *mode = Debug::FRAME_DROPPED_IN_RETURN_CALL;
   } else if (pre_top_frame_code->kind() == Code::STUB &&
       pre_top_frame_code->major_key()) {
     // Entry from our unit tests, it's fine, we support this case.