Alloc stack using MemMap and -Xss

Change-Id: Ib6d52e41e62bf9cd111b2f03257ead53673d3e81
diff --git a/src/runtime.h b/src/runtime.h
index 0aa0cb5..4a5063c 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -75,7 +75,11 @@
 
   ~Runtime();
 
-  ClassLinker* GetClassLinker() {
+  size_t GetStackSize() const {
+    return stack_size_;
+  }
+
+  ClassLinker* GetClassLinker() const {
     return class_linker_;
   }
 
@@ -86,11 +90,14 @@
  private:
   static void PlatformAbort(const char*, int);
 
-  Runtime() : thread_list_(NULL), class_linker_(NULL) {}
+  Runtime() : stack_size_(0), thread_list_(NULL), class_linker_(NULL) {}
 
   // Initializes a new uninitialized runtime.
   bool Init(const Options& options, bool ignore_unrecognized);
 
+  // The default stack size for managed threads created by the runtime.
+  size_t stack_size_;
+
   ThreadList* thread_list_;
 
   ClassLinker* class_linker_;