Make sure debugger is ready for breakpoins when we process 'debugger' statement.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 2ef40c4edbdc581c2e8877db64859e39b89029af..3866a1e97886c99cd3e0e9b5da7bb1b212c852d0 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -3089,8 +3089,19 @@ void Debug::HandleDebugBreak() {
   bool debug_command_only = isolate_->stack_guard()->CheckDebugCommand() &&
                             !isolate_->stack_guard()->CheckDebugBreak();
 
+  bool is_debugger_statement = !isolate_->stack_guard()->CheckDebugCommand() &&
+                               !isolate_->stack_guard()->CheckDebugBreak();
+
   isolate_->stack_guard()->ClearDebugBreak();
 
+  if (is_debugger_statement) {
+    // If we have been called via 'debugger' Javascript statement,
+    // we might not be prepared for breakpoints.
+    // TODO(dslomov,yangguo): CheckDebugBreak may race with RequestDebugBreak.
+    // Revisit this to clean-up.
+    HandleScope handle_scope(isolate_);
+    PrepareForBreakPoints();
+  }
   ProcessDebugMessages(debug_command_only);
 }