Make ChromeSigninClient check if the passed in process id is valid

chrome/browser/signin/chrome_signin_client.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/signin/chrome_signin_client.h"
 
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/content_settings/cookie_settings.h"
 #include "chrome/browser/net/chrome_cookie_notification_details.h"
 #include "chrome/browser/signin/local_auth.h"
@@ skipping 61 matching lines @@
   DCHECK(host);
   host->AddObserver(this);
   signin_hosts_observed_.insert(host);
 }
 
 void ChromeSigninClient::ClearSigninProcess() {
   signin_host_id_ = ChildProcessHost::kInvalidUniqueID;
 }
 
 bool ChromeSigninClient::IsSigninProcess(int process_id) const {
-  return process_id == signin_host_id_;
+  return process_id != ChildProcessHost::kInvalidUniqueID &&
+         process_id == signin_host_id_;
 }
 
 bool ChromeSigninClient::HasSigninProcess() const {
   return signin_host_id_ != ChildProcessHost::kInvalidUniqueID;
 }
 
 void ChromeSigninClient::RenderProcessHostDestroyed(RenderProcessHost* host) {
   // It's possible we're listening to a "stale" renderer because it was replaced
   // with a new process by process-per-site. In either case, stop observing it,
   // but only reset signin_host_id_ tracking if this was from the current signin
@@ skipping 100 matching lines @@
 
 void ChromeSigninClient::UnregisterForCookieChangedNotification() {
   // Note that it's allowed to call this method multiple times without an
   // intervening call to |RegisterForCookieChangedNotification()|.
   content::Source<Profile> source(profile_);
   if (!registrar_.IsRegistered(
       this, chrome::NOTIFICATION_COOKIE_CHANGED, source))
     return;
   registrar_.Remove(this, chrome::NOTIFICATION_COOKIE_CHANGED, source);
 }