cros: Progress to fingerprint enrollment when user touches FP sensor

Bug: 888704
Change-Id: I3d6ccd1d4d4d19377db2d0698ac403ff79cd40e6
Reviewed-on: https://chromium-review.googlesource.com/1244124
Commit-Queue: Xiaoyin Hu <xiaoyinh@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594480}

chrome/browser/resources/chromeos/login/fingerprint_setup.js

@@ -60,9 +60,13 @@ Polymer({
     },
   },
 
-  /** @override */
-  ready: function() {
+  /*
+   * Overridden from OobeDialogHostBehavior.
+   * @override
+   */
+  onBeforeShow: function() {
     this.showScreen_('setupFingerprint');
+    chrome.send('startEnroll');
   },
 
   focus: function() {
@@ -79,7 +83,8 @@ Polymer({
    */
   onEnrollScanDone: function(scanResult, isComplete, percentComplete) {
     // First tap on the sensor to start fingerprint enrollment.
-    if (this.getActiveScreen_() === this.$.placeFinger) {
+    if (this.getActiveScreen_() === this.$.placeFinger ||
+        this.getActiveScreen_() === this.$.setupFingerprint) {
       this.showScreen_('startFingerprintEnroll');
     }
 
@@ -153,7 +158,6 @@ Polymer({
    */
   onContinueToSensorLocationScreen_: function(e) {
     this.showScreen_('placeFinger');
-    chrome.send('startEnroll');
   },
 
   /**