Migrate NoSafepointScope; add constrained concurrent allocation to unit test

runtime/vm/base_isolate.h

Index: runtime/vm/base_isolate.h
diff --git a/runtime/vm/base_isolate.h b/runtime/vm/base_isolate.h
index fc6de2b153e4c3711daf5ac40acb3a4c86e93760..33c5f4d32e845afa3e98e1feaaad2424ca2f0465 100644
--- a/runtime/vm/base_isolate.h
+++ b/runtime/vm/base_isolate.h
@@ -26,28 +26,6 @@ class BaseIsolate {
   void AssertCurrentThreadIsMutator() const {}
 #endif  // DEBUG
 
-  int32_t no_safepoint_scope_depth() const {
-#if defined(DEBUG)
-    return no_safepoint_scope_depth_;
-#else
-    return 0;
-#endif
-  }
-
-  void IncrementNoSafepointScopeDepth() {
-#if defined(DEBUG)
-    ASSERT(no_safepoint_scope_depth_ < INT_MAX);
-    no_safepoint_scope_depth_ += 1;
-#endif
-  }
-
-  void DecrementNoSafepointScopeDepth() {
-#if defined(DEBUG)
-    ASSERT(no_safepoint_scope_depth_ > 0);
-    no_safepoint_scope_depth_ -= 1;
-#endif
-  }
-
   int32_t no_callback_scope_depth() const {
     return no_callback_scope_depth_;
   }
@@ -69,20 +47,14 @@ class BaseIsolate {
  protected:
   BaseIsolate()
       : mutator_thread_(NULL),
-#if defined(DEBUG)
-        no_safepoint_scope_depth_(0),
-#endif
-        no_callback_scope_depth_(0)
-  {}
+        no_callback_scope_depth_(0) {
+  }
 
   ~BaseIsolate() {
     // Do not delete stack resources: top_resource_ and current_zone_.
   }
 
   Thread* mutator_thread_;
-#if defined(DEBUG)
-  int32_t no_safepoint_scope_depth_;
-#endif
   int32_t no_callback_scope_depth_;
 
  private: