Do not assign positions to parser-generated desugarings.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index f1a6aa1509f04078860bb38ee37e7d3f6da17304..268976af3ddb5416234e77dfe297fadcdfed6c25 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -1868,8 +1868,10 @@ class HGraphBuilder {
 
  protected:
   void SetSourcePosition(int position) {
-    DCHECK(position != RelocInfo::kNoPosition);

[adamk, 2015/03/24 15:57:41]

Was this for/let desugaring really the first place to run into this DCHECK?

[Dmitry Lomov (no reviews), 2015/03/24 16:42:52]

Seems to be. This for/let desugaring added comparisons and hydrogen randomly
calls SetSourcePosition for these nodes. It does not call SetSourcePostition for
other nodes.
The entire notion of source positons is needed for --hydrogen-track-positions
flag, which is mostly unused.

-    position_.set_position(position - start_position_);
+    if (position != RelocInfo::kNoPosition) {
+      position_.set_position(position - start_position_);
+    }
+    // Otherwise position remains unknown.
   }
 
   void EnterInlinedSource(int start_position, int id) {