[debugger] step on every assignment in destructuring bind.

src/parsing/parser.h

Index: src/parsing/parser.h
diff --git a/src/parsing/parser.h b/src/parsing/parser.h
index e3b7e70ae71f379bc8063061fdefdfc434a04861..ae0c7499663bda4d5d81e0035a43281bdf627047 100644
--- a/src/parsing/parser.h
+++ b/src/parsing/parser.h
@@ -1077,7 +1077,9 @@ class Parser : public ParserBase<ParserTraits> {
     void RecurseIntoSubpattern(AstNode* pattern, Expression* value) {
       Expression* old_value = current_value_;
       current_value_ = value;
+      recursion_level_++;
       pattern->Accept(this);
+      recursion_level_--;
       current_value_ = old_value;
     }
 
@@ -1089,6 +1091,7 @@ class Parser : public ParserBase<ParserTraits> {
     bool IsAssignmentContext() const { return IsAssignmentContext(context_); }
     bool IsAssignmentContext(PatternContext c) const;
     bool IsBindingContext(PatternContext c) const;
+    bool IsSubPattern() const { return recursion_level_ > 1; }
     PatternContext SetAssignmentContextIfNeeded(Expression* node);
     PatternContext SetInitializerContextIfNeeded(Expression* node);
 
@@ -1110,6 +1113,7 @@ class Parser : public ParserBase<ParserTraits> {
     const DeclarationDescriptor* descriptor_;
     ZoneList<const AstRawString*>* names_;
     Expression* current_value_;
+    int recursion_level_;
     bool* ok_;
   };