Refactor and cleanup VirtualMemory.

test/cctest/test-code-stubs-ia32.cc

Index: test/cctest/test-code-stubs-ia32.cc
diff --git a/test/cctest/test-code-stubs-ia32.cc b/test/cctest/test-code-stubs-ia32.cc
index 3f621758e3c0e5f9c0955cd1f15deaf2c21eb94d..2fde4a52efa85438a439b079e769fe6f89ed7f47 100644
--- a/test/cctest/test-code-stubs-ia32.cc
+++ b/test/cctest/test-code-stubs-ia32.cc
@@ -47,9 +47,10 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
                                               Register destination_reg) {
   // Allocate an executable page of memory.
   size_t actual_size;
-  byte* buffer = static_cast<byte*>(OS::Allocate(Assembler::kMinimalBufferSize,
-                                                   &actual_size,
-                                                   true));
+  byte* buffer = static_cast<byte*>(VirtualMemory::AllocateRegion(
+          Assembler::kMinimalBufferSize,
+          &actual_size,
+          VirtualMemory::EXECUTABLE));
   CHECK(buffer);
   HandleScope handles(isolate);
   MacroAssembler assm(isolate, buffer, static_cast<int>(actual_size));