Fix background compilation: allocate stubs at safepoint

runtime/vm/virtual_memory_macos.cc

Index: runtime/vm/virtual_memory_macos.cc
diff --git a/runtime/vm/virtual_memory_macos.cc b/runtime/vm/virtual_memory_macos.cc
index f28da352ef30940154baf3b98c23931e187c36ad..2bda0fb6eb128e5e3333e0e57aacacc2e71c0285 100644
--- a/runtime/vm/virtual_memory_macos.cc
+++ b/runtime/vm/virtual_memory_macos.cc
@@ -13,6 +13,9 @@
 #include "platform/assert.h"
 #include "platform/utils.h"
 
+#include "vm/isolate.h"
+#include "vm/thread.h"

[siva, 2016/02/17 21:07:49]

These header files are not included in the other OS files.
Also just 
#include "vm/isolate.h"
should be sufficient as "vm/thread.h" is included inside vm/isolate.h

[srdjan, 2016/02/17 21:15:15]

Removed thread.h; added it to other OS-s as well.

+
 namespace dart {
 
 // standard MAP_FAILED causes "error: use of old-style cast" as it
@@ -80,6 +83,8 @@ bool VirtualMemory::Commit(uword addr, intptr_t size, bool executable) {
 
 
 bool VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
+  ASSERT(Thread::Current()->IsMutatorThread() ||
+         Isolate::Current()->mutator_thread()->IsAtSafepoint());
   uword start_address = reinterpret_cast<uword>(address);
   uword end_address = start_address + size;
   uword page_address = Utils::RoundDown(start_address, PageSize());