Revert of [Parser] Introduce AstStringConstants to share constants across AstValueFactory

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 6e3b9f5bc7bf57c5da6a7b7594de5b3c1ce8d458..fc36de3aa53b0a64f3d1cf51d8636ce14704eacc 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -35,7 +35,6 @@
 
 class AccessCompilerData;
 class AddressToIndexHashMap;
-class AstStringConstants;
 class BasicBlockProfiler;
 class Bootstrapper;
 class CancelableTaskManager;
@@ -1156,10 +1155,6 @@
 
   CancelableTaskManager* cancelable_task_manager() {
     return cancelable_task_manager_;
-  }
-
-  AstStringConstants* ast_string_constants() const {
-    return ast_string_constants_;
   }
 
   interpreter::Interpreter* interpreter() const { return interpreter_; }
@@ -1404,8 +1399,6 @@
   std::unique_ptr<CodeEventDispatcher> code_event_dispatcher_;
   FunctionEntryHook function_entry_hook_;
 
-  AstStringConstants* ast_string_constants_;
-
   interpreter::Interpreter* interpreter_;
 
   CompilerDispatcher* compiler_dispatcher_;