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..25007496c7aeb6a8a16a09c4741b30798b942792 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)
@@ -114,7 +115,7 @@ class OSThread : public BaseThread {
   bool ThreadInterruptsEnabled();
 
   // The currently executing thread, or NULL if not yet initialized.
-  static OSThread* Current() {
+  static OSThread* TryCurrent() {
     BaseThread* thread = GetCurrentTLS();
     OSThread* os_thread = NULL;
     if (thread != NULL) {
@@ -124,7 +125,15 @@ class OSThread : public BaseThread {
         Thread* vm_thread = reinterpret_cast<Thread*>(thread);
         os_thread = GetOSThreadFromThread(vm_thread);
       }
-    } else {
+    }
+    return os_thread;
+  }
+
+  // The currently executing thread. If there is no currently executing thread,
+  // a new OSThread is created and returned.
+  static OSThread* Current() {
+    OSThread* os_thread = TryCurrent();
+    if (os_thread == NULL) {
       os_thread = CreateAndSetUnknownThread();
     }
     return os_thread;