Debugger: correctly break in default constructor.

src/full-codegen/full-codegen.cc

Index: src/full-codegen/full-codegen.cc
diff --git a/src/full-codegen/full-codegen.cc b/src/full-codegen/full-codegen.cc
index 008be18e363ecb52a8e36716f25c62c9484543a9..1d8c8b37b96879b5f8a0ef7542e70602a7bd62d6 100644
--- a/src/full-codegen/full-codegen.cc
+++ b/src/full-codegen/full-codegen.cc
@@ -560,7 +560,10 @@ void FullCodeGenerator::SetFunctionPosition(FunctionLiteral* fun) {
 
 
 void FullCodeGenerator::SetReturnPosition(FunctionLiteral* fun) {
-  RecordStatementPosition(masm_, fun->end_position() - 1);
+  // For default constructors, start position equals end position, and there
+  // is no source code besides the class literal.
+  int pos = std::max(fun->start_position(), fun->end_position() - 1);
+  RecordStatementPosition(masm_, pos);
   if (info_->is_debug()) {
     // Always emit a debug break slot before a return.
     DebugCodegen::GenerateSlot(masm_, RelocInfo::DEBUG_BREAK_SLOT_AT_RETURN);