Remove extra assignment to gwtOnLoad (#10061)

Only saves about 10 bytes per GWT application, but the extra assignment
appears to serve no purpose. Also corrects some slightly inaccurate
comments about how initialization behaves.

Fixes #10060

dev/core/src/com/google/gwt/dev/jjs/impl/GenerateJavaScriptAST.java

@@ -1962,10 +1962,10 @@ private void markPosition(String name, Type type) {
      * source loading and runs in the global scope (not inside of any function scope).
      */
     private void setupGwtOnLoad() {
-      /**
+      /*
        * <pre>
-       * var $entry = Impl.registerEntry();
-       * var gwtOnLoad = ModuleUtils.gwtOnLoad();
+       * var $entry = ModuleUtils.registerEntry();
+       * var gwtOnLoad = ModuleUtils.gwtOnLoad;
        * ModuleUtils.addInitFunctions(init1, init2,...)
        * </pre>
        */
@@ -1980,8 +1980,8 @@ private void setupGwtOnLoad() {
       // var gwtOnLoad = ModuleUtils.gwtOnLoad;
       JsName gwtOnLoad = topScope.findExistingUnobfuscatableName("gwtOnLoad");
       JsVar varGwtOnLoad = new JsVar(sourceInfo, gwtOnLoad);
-      varGwtOnLoad.setInitExpr(createAssignment(gwtOnLoad.makeRef(sourceInfo),
-          getIndexedMethodJsName(RuntimeConstants.MODULE_UTILS_GWT_ON_LOAD).makeRef(sourceInfo)));
+      varGwtOnLoad.setInitExpr(
+          getIndexedMethodJsName(RuntimeConstants.MODULE_UTILS_GWT_ON_LOAD).makeRef(sourceInfo));
       getGlobalStatements().add(new JsVars(sourceInfo, varGwtOnLoad));
 
       // ModuleUtils.addInitFunctions(init1, init2,...)