Add for-of Crankshaft support

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 62c6073a2fe96c333f07192ac156ed8b88aaa048..2c4a8042c31c50d22d6264cb4d94a5108df10f8c 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -1239,16 +1239,6 @@ void FullCodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
   __ CompareRoot(rax, Heap::kNullValueRootIndex);
   __ j(equal, loop_statement.break_label());
 
-  // Convert the iterator to a JS object.
-  Label convert, done_convert;
-  __ JumpIfSmi(rax, &convert);
-  __ CmpObjectType(rax, FIRST_SPEC_OBJECT_TYPE, rcx);
-  __ j(above_equal, &done_convert);
-  __ bind(&convert);
-  __ push(rax);
-  __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
-  __ bind(&done_convert);
-
   // Loop entry.
   __ bind(loop_statement.continue_label());
 
@@ -1263,14 +1253,15 @@ void FullCodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
                   &result_not_done);
   __ bind(&result_not_done);
 
+  PrepareForBailoutForId(stmt->BodyId(), NO_REGISTERS);
+
   // each = result.value
   VisitForEffect(stmt->assign_each());
 
   // Generate code for the body of the loop.
   Visit(stmt->body());
 
-  // Check stack before looping.
-  PrepareForBailoutForId(stmt->BackEdgeId(), NO_REGISTERS);
+  // Loop.
   EmitBackEdgeBookkeeping(stmt, loop_statement.continue_label());
   __ jmp(loop_statement.continue_label());