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

src/full-codegen/ia32/full-codegen-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_IA32
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 1053 matching lines @@
   // permanent slow case into register edx.
   __ mov(edx, Operand(esp, 3 * kPointerSize));
 
   // Check if the expected map still matches that of the enumerable.
   // If not, we may have to filter the key.
   Label update_each;
   __ mov(ecx, Operand(esp, 4 * kPointerSize));
   __ cmp(edx, FieldOperand(ecx, 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.
-  DCHECK(Smi::FromInt(0) == 0);
-  __ test(edx, edx);
-  __ j(zero, &update_each);
-
   // 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.
   __ push(ecx);  // Enumerable.
   __ push(ebx);  // Current entry.
   __ CallRuntime(Runtime::kForInFilter, 2);
   PrepareForBailoutForId(stmt->FilterId(), TOS_REG);
   __ cmp(eax, isolate()->factory()->undefined_value());
   __ j(equal, loop_statement.continue_label());
   __ mov(ebx, eax);
@@ skipping 3734 matching lines @@
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32