[proxy] fixing harmony/proxy.js tests and improving error messages + some drive-by fixes

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index 961cefa4f52404982174e120bc40ede50f7e1538..74ad7cb1e0d7f2fd8ccbe007be62a14870740765 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -1048,7 +1048,6 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   __ jmp(&exit);
 
   // We got a fixed array in register rax. Iterate through that.
-  Label non_proxy;
   __ bind(&fixed_array);
 
   // No need for a write barrier, we are storing a Smi in the feedback vector.
@@ -1056,14 +1055,8 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   int vector_index = SmiFromSlot(slot)->value();
   __ Move(FieldOperand(rbx, FixedArray::OffsetOfElementAt(vector_index)),
           TypeFeedbackVector::MegamorphicSentinel(isolate()));
-  __ Move(rbx, Smi::FromInt(1));  // Smi indicates slow check
   __ movp(rcx, Operand(rsp, 0 * kPointerSize));  // Get enumerated object
-  STATIC_ASSERT(JS_PROXY_TYPE == FIRST_JS_RECEIVER_TYPE);
-  __ CmpObjectType(rcx, JS_PROXY_TYPE, rcx);
-  __ j(above, &non_proxy);
-  __ Move(rbx, Smi::FromInt(0));  // Zero indicates proxy
-  __ bind(&non_proxy);
-  __ Push(rbx);  // Smi
+  __ Push(Smi::FromInt(1));                      // Smi(1) indicates slow check
   __ Push(rax);  // Array
   __ movp(rax, FieldOperand(rax, FixedArray::kLengthOffset));
   __ Push(rax);  // Fixed array length (as smi).
@@ -1096,11 +1089,6 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   __ cmpp(rdx, FieldOperand(rcx, HeapObject::kMapOffset));
   __ j(equal, &update_each, Label::kNear);
 
-  // For proxies, no filtering is done.
-  // TODO(rossberg): What if only a prototype is a proxy? Not specified yet.
-  __ Cmp(rdx, Smi::FromInt(0));
-  __ j(equal, &update_each, Label::kNear);
-
   // Convert the entry to a string or null if it isn't a property
   // anymore. If the property has been removed while iterating, we
   // just skip it.