Fix typo in host_installer.js

remoting/webapp/host_installer.js

Index: remoting/webapp/host_installer.js
diff --git a/remoting/webapp/host_installer.js b/remoting/webapp/host_installer.js
index 6983a5679176446cd4e636795bd2c3c9fb621c90..48e62a2cbad4ef956c49c1bb5839fdf8ba4c2782 100644
--- a/remoting/webapp/host_installer.js
+++ b/remoting/webapp/host_installer.js
@@ -128,7 +128,7 @@ remoting.HostInstaller.prototype.downloadAndWaitForInstall = function() {
       return Promise.resolve(true);
     }
 
-    if (that.downloadAndWaitForInstallPromise_ !== null) {
+    if (that.downloadAndWaitForInstallPromise_ === null) {
       that.downloadAndWaitForInstallPromise_ = new Promise(
         /** @param {Function} resolve */
         function(resolve){
@@ -160,4 +160,4 @@ remoting.HostInstaller.prototype.cancel = function() {
     this.checkInstallIntervalId_ = null;
   }
   this.downloadAndWaitForInstallPromise_ = null;
-};
+};