[debugger] Hide scopes that originate from desugaring.

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index dae70c0142b1e2785833fb75f8f34af9ee26a0ed..52fc789866a44e2f026b99b727ec2356e4b35644 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -295,6 +295,10 @@ class Scope: public ZoneObject {
     end_position_ = statement_pos;
   }
 
+  // Scopes created for desugaring are hidden. I.e. not visible to the debugger.
+  bool is_hidden() const { return is_hidden_; }
+  void set_is_hidden() { is_hidden_ = true; }
+
   // In some cases we want to force context allocation for a whole scope.
   void ForceContextAllocation() {
     DCHECK(!already_resolved());
@@ -574,6 +578,9 @@ class Scope: public ZoneObject {
 
 #ifdef DEBUG
   void Print(int n = 0);  // n = indentation; n < 0 => don't print recursively
+
+  // Check that the scope has positions assigned.
+  void CheckScopePositions();
 #endif
 
   // ---------------------------------------------------------------------------
@@ -645,6 +652,7 @@ class Scope: public ZoneObject {
   // Source positions.
   int start_position_;
   int end_position_;
+  bool is_hidden_;
 
   // Computed via PropagateScopeInfo.
   bool outer_scope_calls_sloppy_eval_;