Move no_callback_scope_depth_ and cha_ from isolate -> thread

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 33c5f4d32e845afa3e98e1feaaad2424ca2f0465..833f7e5ec7dbb7d35263530448288e8a7f5aece6 100644
--- a/runtime/vm/base_isolate.h
+++ b/runtime/vm/base_isolate.h
@@ -26,28 +26,13 @@ class BaseIsolate {
   void AssertCurrentThreadIsMutator() const {}
 #endif  // DEBUG
 
-  int32_t no_callback_scope_depth() const {
-    return no_callback_scope_depth_;
-  }
-
-  void IncrementNoCallbackScopeDepth() {
-    ASSERT(no_callback_scope_depth_ < INT_MAX);
-    no_callback_scope_depth_ += 1;
-  }
-
-  void DecrementNoCallbackScopeDepth() {
-    ASSERT(no_callback_scope_depth_ > 0);
-    no_callback_scope_depth_ -= 1;
-  }
-
 #if defined(DEBUG)
   static void AssertCurrent(BaseIsolate* isolate);
 #endif
 
  protected:
   BaseIsolate()
-      : mutator_thread_(NULL),
-        no_callback_scope_depth_(0) {
+      : mutator_thread_(NULL) {
   }
 
   ~BaseIsolate() {
@@ -55,7 +40,6 @@ class BaseIsolate {
   }
 
   Thread* mutator_thread_;
-  int32_t no_callback_scope_depth_;
 
  private:
   // During migration, some deprecated interfaces will default to using the