[chromedriver] Fix javascript check node is reachable for Proxy

The root level node could be a javascript Proxy
object(https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy)
instead of the document itself. In this case, we cannot use "==
document" to check if an element is reachable and generate the stale element
error. Instead, we will use "== document.documentElement.parentNode",
which should be document or the Proxy node.

Bug: chromedriver:3628
Change-Id: Ie7c7c78e0e796dcf3023aa1d5385fa95bd139ba0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2502576Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Shengfa Lin <shengfa@google.com>
Cr-Commit-Position: refs/heads/master@{#821428}

chrome/test/chromedriver/js/call_function.js

@@ -134,7 +134,7 @@ CacheWithUUID.prototype = {
     */
   isNodeReachable_: function(node) {
     var nodeRoot = getNodeRootThroughAnyShadows(node);
-    return (nodeRoot == document);
+    return (nodeRoot == document.documentElement.parentNode);
   }
 
 
@@ -202,7 +202,7 @@ Cache.prototype = {
     */
   isNodeReachable_: function(node) {
     var nodeRoot = getNodeRootThroughAnyShadows(node);
-    return (nodeRoot == document);
+    return (nodeRoot == document.documentElement.parentNode);
   }
 };