Revert "Fix leftover usage of OS::Allocate()."

TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23691049

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16664 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/codegen-x64.cc

@@ -159,10 +159,9 @@ typedef double (*ModuloFunction)(double, double);
 // Define custom fmod implementation.
 ModuloFunction CreateModuloFunction() {
   size_t actual_size;
-  byte* buffer = static_cast<byte*>(VirtualMemory::AllocateRegion(
-          Assembler::kMinimalBufferSize,
-          &actual_size,
-          VirtualMemory::EXECUTABLE));
+  byte* buffer = static_cast<byte*>(OS::Allocate(Assembler::kMinimalBufferSize,
+                                                 &actual_size,
+                                                 true));
   CHECK(buffer);
   Assembler masm(NULL, buffer, static_cast<int>(actual_size));
   // Generated code is put into a fixed, unmovable, buffer, and not into