Change PeepholeRemoveDeadCode to stop asserting that the AST is norma…

…lized.

The pass runs both before and after denormalize. So it’s a bug that the pass unconditionally asserts that the AST is normalized.

This CL deletes the check. Alternatively, even just guarding the check with `isASTNormalized` would works - http://sponge2/c65113df-4f96-4148-9400-6f551562349c

```
        if (!isASTNormalized()) {
          // the pass is running after denormalize
          return subtree;
        }
        throw checkNormalization(false, "WHILE");
```

PiperOrigin-RevId: 561471939

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

@@ -58,7 +58,10 @@ Node optimizeSubtree(Node subtree) {
       case IF:
         return tryFoldIf(subtree);
       case WHILE:
-        throw checkNormalization(false, "WHILE");
+        // This pass gets run both before and after denormalize. Hence, the AST could potentially
+        // contain WHILE (denormalized).
+        // TODO: Ideally, we should optimize this case instead of returning
+        return subtree;
       case FOR:
         {
           Node condition = NodeUtil.getConditionExpression(subtree);
@@ -787,7 +790,6 @@ Node tryOptimizeBlock(Node n) {
     for (Node c = n.getFirstChild(); c != null; ) {
       Node next = c.getNext();  // save c.next, since 'c' may be removed
       if (!isUnremovableNode(c) && !mayHaveSideEffects(c)) {
-        checkNormalization(!NodeUtil.isFunctionDeclaration(n), "function declaration");
         // TODO(johnlenz): determine what this is actually removing. Candidates
         //    include: EMPTY nodes, control structures without children
         //    (removing infinite loops), empty try blocks.  What else?
@@ -1377,10 +1379,4 @@ private Node tryRemoveOptionalCall(Node optionalCall) {
     this.reportChangeToEnclosingScope(result);
     return result;
   }
-
-  private static @Nullable IllegalStateException checkNormalization(
-      boolean condition, String feature) {
-    checkState(condition, "Unexpected %s. AST should be normalized.", feature);
-    return null;
-  }
 }

test/com/google/javascript/jscomp/PeepholeRemoveDeadCodeTest.java

@@ -55,6 +55,9 @@ public void process(Node externs, Node root) {
   @Before
   public void setUp() throws Exception {
     super.setUp();
+    // This pass doesn't need the AST to be normalized as it runs both before and after
+    // `denormalize`. Since it runs PureFunctionsIdentifier pass which expects the AST to be
+    // normalized, we're doing `enableNormalize` for these tests.
     enableNormalize();
     // TODO(bradfordcsmith): Stop normalizing the expected output or document why it is necessary.
     enableNormalizeExpectedOutput();