Migrate NoSafepointScope; add constrained concurrent allocation to unit test

runtime/vm/thread.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_THREAD_H_
 #define VM_THREAD_H_
 
 #include "vm/globals.h"
 #include "vm/os_thread.h"
 #include "vm/store_buffer.h"
@@ skipping 135 matching lines @@
     return 0;
 #endif
   }
 
   void set_top_handle_scope(HandleScope* handle_scope) {
 #if defined(DEBUG)
     state_.top_handle_scope = handle_scope;
 #endif
   }
 
+  int32_t no_safepoint_scope_depth() const {
+#if defined(DEBUG)
+    return state_.no_safepoint_scope_depth;
+#else
+    return 0;
+#endif
+  }
+
+  void IncrementNoSafepointScopeDepth() {
+#if defined(DEBUG)
+    ASSERT(state_.no_safepoint_scope_depth < INT_MAX);
+    state_.no_safepoint_scope_depth += 1;
+#endif
+  }
+
+  void DecrementNoSafepointScopeDepth() {
+#if defined(DEBUG)
+    ASSERT(state_.no_safepoint_scope_depth > 0);
+    state_.no_safepoint_scope_depth -= 1;
+#endif
+  }
+
   // Collection of isolate-specific state of a thread that is saved/restored
   // on isolate exit/re-entry.
   struct State {
     Zone* zone;
     uword top_exit_frame_info;
     StackResource* top_resource;
 #if defined(DEBUG)
     HandleScope* top_handle_scope;
     intptr_t no_handle_scope_depth;
+    int32_t no_safepoint_scope_depth;
 #endif
   };
 
 #define DEFINE_OFFSET_METHOD(type_name, member_name, expr, default_init_value) \
   static intptr_t member_name##offset() {                                      \
     return OFFSET_OF(Thread, member_name);                                     \
   }
 CACHED_CONSTANTS_LIST(DEFINE_OFFSET_METHOD)
 #undef DEFINE_OFFSET_METHOD
 
@@ skipping 33 matching lines @@
   void Unschedule();
 
   friend class Isolate;
   friend class StackZone;
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace dart
 
 #endif  // VM_THREAD_H_