Get rid of unused field has_compiled_code_ from the Isolate structure.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 8f06434fe7ec1c4f97cf93c7cd5638996af4a081..1b22da28e09ae60c255317aa34d08ebb563e51c7 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -1161,8 +1161,6 @@ bool CompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
           // }
         }
       }
-      // Mark that this isolate now has compiled code.
-      isolate()->set_has_compiled_code(true);
       // Exit the loop and the function with the correct result value.
       is_compiled = true;
       done = true;