Remove unused methods from TranspilationPasses

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188271287

src/com/google/javascript/jscomp/TranspilationPasses.java

@@ -412,48 +412,6 @@ static boolean isScriptEs6OrHigher(Node script) {
     return features != null && !FeatureSet.ES5.contains(features);
   }
 
-  /**
-   * Process checks if the input language contains the provided features, on any JS file that has
-   * ES6 features.
-   *
-   * @param compiler An AbstractCompiler
-   * @param combinedRoot The combined root for all JS files.
-   * @param featureSet The features which this check targets.
-   * @param callbacks The callbacks that should be invoked if a file has ES6 features.
-   */
-  static void processCheck(
-      AbstractCompiler compiler, Node combinedRoot, FeatureSet featureSet, Callback... callbacks) {
-    if (compiler.getOptions().getLanguageIn().toFeatureSet().contains(featureSet)) {
-      for (Node singleRoot : combinedRoot.children()) {
-        if (isScriptEs6OrHigher(singleRoot)) {
-          for (Callback callback : callbacks) {
-            NodeTraversal.traverseEs6(compiler, singleRoot, callback);
-          }
-        }
-      }
-    }
-  }
-
-  /**
-   * Hot-swap ES6+ checks if the input language contains the provided features, on any JS file that
-   * has ES6 features.
-   *
-   * @param compiler An AbstractCompiler
-   * @param scriptRoot The SCRIPT root for the JS file.
-   * @param featureSet The features which this check targets.
-   * @param callbacks The callbacks that should be invoked if the file has ES6 features.
-   */
-  static void hotSwapCheck(
-      AbstractCompiler compiler, Node scriptRoot, FeatureSet featureSet, Callback... callbacks) {
-    if (compiler.getOptions().getLanguageIn().toFeatureSet().contains(featureSet)) {
-      if (isScriptEs6OrHigher(scriptRoot)) {
-        for (Callback callback : callbacks) {
-          NodeTraversal.traverseEs6(compiler, scriptRoot, callback);
-        }
-      }
-    }
-  }
-
   /**
    * Process transpilations if the input language needs transpilation from certain features, on any
    * JS file that has ES6 features.