Debugger: use correct position for for-next expression statement.

R=rossberg@chromium.org
BUG=chromium:523543
LOG=N

Review URL: https://codereview.chromium.org/1310213002

Cr-Commit-Position: refs/heads/master@{#30328}

src/parser.cc

@@ -3752,9 +3752,8 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
 
   Statement* next = NULL;
   if (peek() != Token::RPAREN) {
-    int next_pos = position();
     Expression* exp = ParseExpression(true, CHECK_OK);
-    next = factory()->NewExpressionStatement(exp, next_pos);
+    next = factory()->NewExpressionStatement(exp, exp->position());
   }
   Expect(Token::RPAREN, CHECK_OK);
 

test/mjsunit/es6/debug-stepnext-for.js

@@ -106,11 +106,11 @@ var expected = [
   // For-of-let: next(), body, next(), ...
   "j16","J4","j16","J4","j16","J4","j16",
   // For-var: var decl, condition, body, next, condition, body, ...
-  "k7","k20","K4","k23","k20","K4","k23","k20","K4","k23","k20",
+  "k7","k20","K4","k26","k20","K4","k26","k20","K4","k26","k20",
   // For: init, condition, body, next, condition, body, ...
-  "l7","l16","L4","l19","l16","L4","l19","l16","L4","l19","l16",
+  "l7","l16","L4","l22","l16","L4","l22","l16","L4","l22","l16",
   // For-let: init, condition, body, next, condition, body, ...
-  "m7","m20","M4","m23","m20","M4","m23","m20","M4","m23","m20",
+  "m7","m20","M4","m26","m20","M4","m26","m20","M4","m26","m20",
   // Exit.
   "y0","z0",
 ]

test/mjsunit/es6/regress/regress-468661.js

@@ -63,8 +63,8 @@ var sum = 0;
   debugger; // Break 0.
 
   for (let i=0; // Break 1.
-       i < 1;   // Break 2. // Break 5. // Break 6.
-       i++) {
+       i < 1;   // Break 2.  // Break 6.
+       i++) {   // Break 5.
     let key = i; // Break 3.
     sum += key;   // Break 4.
   }