Implement Smart Pipeline proposal in @babel/parser

packages/babel-parser/src/tokenizer/state.js

@@ -33,6 +33,12 @@ export default class State {
     this.hasFlowComment = false;
     this.isIterator = false;
 
+    // Used by smartPipelines.
+    this.topicContextState = {
+      maxNumOfResolvableTopics: 0,
+      maxTopicIndex: undefined,
+    };
+
     this.classLevel = 0;
 
     this.labels = [];
@@ -111,6 +117,9 @@ export default class State {
   hasFlowComment: boolean;
   isIterator: boolean;
 
+  // For the smartPipelines plugin:
+  topicContextState: tt.TopicContextState;
+
   // Check whether we are in a (nested) class or not.
   classLevel: number;