[es6] Fix bug in pattern re-writing

src/parsing/pattern-rewriter.cc

Index: src/parsing/pattern-rewriter.cc
diff --git a/src/parsing/pattern-rewriter.cc b/src/parsing/pattern-rewriter.cc
index 3ecffb99dbd763f26a5a13756092fb5e8006a64b..1d93271e6e72d3f2e7257340d7ffb3e367278fb3 100644
--- a/src/parsing/pattern-rewriter.cc
+++ b/src/parsing/pattern-rewriter.cc
@@ -79,7 +79,11 @@ bool Parser::PatternRewriter::IsBindingContext(PatternContext c) const {
 Parser::PatternRewriter::PatternContext
 Parser::PatternRewriter::SetAssignmentContextIfNeeded(Expression* node) {
   PatternContext old_context = context();
-  if (node->IsAssignment() && node->AsAssignment()->op() == Token::ASSIGN) {
+  // AssignmentExpressions may occur in the Initializer position of a
+  // SingleNameBinding. Such expressions should not prompt a change in the
+  // pattern's context.
+  if (node->IsAssignment() && node->AsAssignment()->op() == Token::ASSIGN &&
+      !IsInitializerContext()) {
     set_context(ASSIGNMENT);
   }
   return old_context;