Port r10023 to x64 (Add pointer cache field to external string).

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
diff --git a/src/ia32/codegen-ia32.cc b/src/ia32/codegen-ia32.cc
index 58eead772b067f9c5f550b0b53b2d18ba9d90f92..55ef237011014d927ab6754ccffceda63923a2bd 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -559,11 +559,11 @@ void StringCharLoadGenerator::Generate(MacroAssembler* masm,
   if (FLAG_debug_code) {
     // Assert that we do not have a cons or slice (indirect strings) here.
     // Sequential strings have already been ruled out.
-    __ test(result, Immediate(kIsIndirectStringMask));
+    __ test_b(result, Immediate(kIsIndirectStringMask));
     __ Assert(zero, "external string expected, but not found");
   }
   __ mov(result, FieldOperand(string, ExternalString::kResourceDataOffset));
-  // Assert that the external string has not been finalized yet.
+  // Assert that the data pointer cache is valid.
   __ test(result, result);
   __ j(zero, call_runtime);
   Register scratch = string;