Replace 'for(int i)' loop with 'for each' for better performance.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=242520832

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

@@ -1054,8 +1054,9 @@ private void popScope(boolean quietly) {
   public AbstractScope<?, ?> getAbstractScope() {
     AbstractScope<?, ?> scope = scopes.peek();
 
-    for (int i = 0; i < scopeRoots.size(); i++) {
-      scope = scopeCreator.createScope(scopeRoots.get(i), scope);
+    // NOTE(dylandavidson): Use for-each loop to avoid slow ArrayList#get performance.
+    for (Node scopeRoot : scopeRoots) {
+      scope = scopeCreator.createScope(scopeRoot, scope);
       scopes.push(scope);
     }
     scopeRoots.clear();