Add parser support for generators.

src/full-codegen.cc

Index: src/full-codegen.cc
diff --git a/src/full-codegen.cc b/src/full-codegen.cc
index a43f674c33641f1ae9682423494f2c76b9f744e1..f141438ac5e4bbe0b8c4af91eb9b44c62d7618f6 100644
--- a/src/full-codegen.cc
+++ b/src/full-codegen.cc
@@ -232,6 +232,12 @@ void BreakableStatementChecker::VisitAssignment(Assignment* expr) {
 }
 
 
+void BreakableStatementChecker::VisitYield(Yield* expr) {
+  // Yield is breakable if the expression is.
+  Visit(expr->expression());
+}
+
+
 void BreakableStatementChecker::VisitThrow(Throw* expr) {
   // Throw is breakable if the expression is.
   Visit(expr->exception());
@@ -1537,6 +1543,28 @@ void FullCodeGenerator::VisitSharedFunctionInfoLiteral(
 }
 
 
+void FullCodeGenerator::VisitYield(Yield* expr) {
+  if (expr->is_delegating_yield())
+    UNIMPLEMENTED();
+
+  Comment cmnt(masm_, "[ Yield");
+  VisitForAccumulatorValue(expr->expression());
+  // TODO(wingo): Assert that the operand stack depth is 0, at least while
+  // general yield expressions are unimplemented.
+
+  // TODO(wingo): What follows is as in VisitReturnStatement.  Replace it with a
+  // call to a builtin that will resume the generator.
+  NestedStatement* current = nesting_stack_;
+  int stack_depth = 0;
+  int context_length = 0;
+  while (current != NULL) {
+    current = current->Exit(&stack_depth, &context_length);
+  }
+  __ Drop(stack_depth);
+  EmitReturnSequence();
+}
+
+
 void FullCodeGenerator::VisitThrow(Throw* expr) {
   Comment cmnt(masm_, "[ Throw");
   VisitForStackValue(expr->exception());