In order to simplify m-c code, move some in pdf.js

* move set/clear|Timeout/Interval and crackURL code in pdf.js
 * remove the "backdoor" in the proxy (used to dispatch event) and so return the dispatch function in the initializer
 * remove listeners if an error occured during sandbox initialization
 * add support for alert and prompt in the sandbox
 * add a function to eval in the global scope

web/ui_utils.js

@@ -1015,42 +1015,6 @@ function getActiveOrFocusedElement() {
   return curActiveOrFocused;
 }
 
-/**
- * Generate a random string which is not define somewhere in actions.
- *
- * @param {Object} objects - The value returned by `getFieldObjects` in the API.
- * @returns {string} A unique string.
- */
-function generateRandomStringForSandbox(objects) {
-  const allObjects = Object.values(objects).flat(2);
-  const actions = allObjects
-    .filter(obj => !!obj.actions)
-    .map(obj => Object.values(obj.actions))
-    .flat(2);
-
-  while (true) {
-    const name = new Uint8Array(64);
-    if (typeof crypto !== "undefined") {
-      crypto.getRandomValues(name);
-    } else {
-      for (let i = 0, ii = name.length; i < ii; i++) {
-        name[i] = Math.floor(256 * Math.random());
-      }
-    }
-
-    const nameString =
-      "_" +
-      btoa(
-        Array.from(name)
-          .map(x => String.fromCharCode(x))
-          .join("")
-      );
-    if (actions.every(action => !action.includes(nameString))) {
-      return nameString;
-    }
-  }
-}
-
 export {
   AutoPrintRegExp,
   CSS_UNITS,
@@ -1074,7 +1038,6 @@ export {
   NullL10n,
   EventBus,
   ProgressBar,
-  generateRandomStringForSandbox,
   getPDFFileNameFromURL,
   noContextMenuHandler,
   parseQueryString,