Revert "[Arguments] Merge (7442,7496] from bleeding_edge."

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index c4b0fb8226e79e98d2a1d30a4dd565b56b569e53..9cf8b57e178304096b42fa70f3d1fddd19db9569 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -215,14 +215,13 @@ OS::MemCopyFunction CreateMemCopyFunction();
 void OS::MemCopy(void* dest, const void* src, size_t size) {
   if (memcopy_function == NULL) {
     ScopedLock lock(memcopy_function_mutex);
+    Isolate::EnsureDefaultIsolate();
     if (memcopy_function == NULL) {
       OS::MemCopyFunction temp = CreateMemCopyFunction();
       MemoryBarrier();
       memcopy_function = temp;
     }
   }
-  // Note: here we rely on dependent reads being ordered. This is true
-  // on all architectures we currently support.
   (*memcopy_function)(dest, src, size);
 #ifdef DEBUG
   CHECK_EQ(0, memcmp(dest, src, size));