Remove some Isolate::current_zone() calls, as it gets the zone from mutator thread not the current …

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 6655af303bb89fda05a02c6a3a3da60a6eca7891..f534b8cb1f9763139353e621bf58968d3a313855 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -1553,7 +1553,7 @@ void BackgroundCompiler::EnsureInit(Isolate* isolate) {
       BackgroundCompiler* task = new BackgroundCompiler(isolate);
       isolate->set_background_compiler(task);
       isolate->set_background_compilation_queue(GrowableObjectArray::Handle(
-          isolate->current_zone(), GrowableObjectArray::New()));
+          GrowableObjectArray::New()));
       start_task = true;
     }
   }