Updated MallocHooks to collect stack traces when memory is allocated.

runtime/vm/os_thread.h

Index: runtime/vm/os_thread.h
diff --git a/runtime/vm/os_thread.h b/runtime/vm/os_thread.h
index da298316dd60bd29c673b2754365830eaa462ad1..1312431fad5024b54f313002c5b42a4a9ba52a5c 100644
--- a/runtime/vm/os_thread.h
+++ b/runtime/vm/os_thread.h
@@ -8,6 +8,7 @@
 #include "platform/globals.h"
 #include "vm/allocation.h"
 #include "vm/globals.h"
+#include "vm/malloc_hooks.h"
 
 // Declare the OS-specific types ahead of defining the generic classes.
 #if defined(TARGET_OS_ANDROID)
@@ -113,6 +114,8 @@ class OSThread : public BaseThread {
   void EnableThreadInterrupts();
   bool ThreadInterruptsEnabled();
 
+  static bool DoesCurrentThreadExist() { return (GetCurrentTLS() != NULL); }
+
   // The currently executing thread, or NULL if not yet initialized.
   static OSThread* Current() {
     BaseThread* thread = GetCurrentTLS();