[debugger] Hide scopes that originate from desugaring.

test/mjsunit/es6/debug-blockscopes.js

Index: test/mjsunit/es6/debug-blockscopes.js
diff --git a/test/mjsunit/es6/debug-blockscopes.js b/test/mjsunit/es6/debug-blockscopes.js
index 193ad705cb339732f4310adb7c0546373db6157e..87dd1b66c889d50a63d431375694573309622ff7 100644
--- a/test/mjsunit/es6/debug-blockscopes.js
+++ b/test/mjsunit/es6/debug-blockscopes.js
@@ -52,6 +52,7 @@ function listener(event, exec_state, event_data, data) {
       listener_delegate(exec_state);
     }
   } catch (e) {
+    print(e, e.stack);
     exception = e;
   }
 }
@@ -380,16 +381,12 @@ function for_loop_1() {
 
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
-                   debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
   CheckScopeContent({x:'y'}, 0, exec_state);
   // The function scope contains a temporary iteration variable, but it is
   // hidden to the debugger.
-  // TODO(adamk): This variable is only used to provide a TDZ for the enumerable
-  // expression and should not be visible to the debugger.
-  CheckScopeContent({x:undefined}, 1, exec_state);
 };
 for_loop_1();
 EndTest();
@@ -409,7 +406,6 @@ function for_loop_2() {
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
                    debug.ScopeType.Block,
-                   debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
@@ -417,9 +413,6 @@ listener_delegate = function(exec_state) {
   CheckScopeContent({x:'y'}, 1, exec_state);
   // The function scope contains a temporary iteration variable, hidden to the
   // debugger.
-  // TODO(adamk): This variable is only used to provide a TDZ for the enumerable
-  // expression and should not be visible to the debugger.
-  CheckScopeContent({x:undefined}, 2, exec_state);
 };
 for_loop_2();
 EndTest();
@@ -436,13 +429,11 @@ function for_loop_3() {
 
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
-                   debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
   CheckScopeContent({x:3}, 0, exec_state);
-  CheckScopeContent({x:3}, 1, exec_state);
-  CheckScopeContent({}, 2, exec_state);
+  CheckScopeContent({}, 1, exec_state);
 };
 for_loop_3();
 EndTest();
@@ -461,14 +452,12 @@ function for_loop_4() {
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
                    debug.ScopeType.Block,
-                   debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
   CheckScopeContent({x:5}, 0, exec_state);
   CheckScopeContent({x:3}, 1, exec_state);
-  CheckScopeContent({x:3}, 2, exec_state);
-  CheckScopeContent({}, 3, exec_state);
+  CheckScopeContent({}, 2, exec_state);
 };
 for_loop_4();
 EndTest();
@@ -485,13 +474,11 @@ function for_loop_5() {
 
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
-                   debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
   CheckScopeContent({x:3,y:5}, 0, exec_state);
-  CheckScopeContent({x:3,y:5}, 1, exec_state);
-  CheckScopeContent({}, 2, exec_state);
+  CheckScopeContent({}, 1, exec_state);
 };
 for_loop_5();
 EndTest();