settings: Issues with confirming PIN on lock screen.

This CL does:
1) Keeps the confirm button disabled until something has been entered.
2) Enables the confirm button after a new digit has been pressed after a wrong PIN has been entered.
3) Focuses and highlights the wrong PIN after one has been entered.

Test: browser_tests "CrSettingsPeoplePageSetupPinDialogTest.*"
Bug: 751079,751312
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ife71bc02f6955a819cbb65f9d937eb6dd4a78863
Reviewed-on: https://chromium-review.googlesource.com/596922Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491512}

chrome/browser/resources/settings/people_page/setup_pin_dialog.js

@@ -256,10 +256,7 @@ Polymer({
     }
 
     this.hideProblem_();
-    if (this.canSubmit_()) {
-      this.enableSubmit_ = true;
-      return;
-    }
+    this.enableSubmit_ = this.pinKeyboardValue_.length > 0;
   },
 
   /** @private */
@@ -277,6 +274,9 @@ Polymer({
     // The PIN is not guaranteed to be valid in that case.
     if (!this.canSubmit_()) {
       this.showProblem_(MessageType.MISMATCH, ProblemType.ERROR);
+      this.enableSubmit_ = false;
+      // Focus the PIN keyboard and highlight the entire PIN.
+      this.$.pinKeyboard.focus(0, this.pinKeyboardValue_.length + 1);
       return;
     }
 

chrome/test/data/webui/settings/quick_unlock_authenticate_browsertest_chromeos.js

@@ -500,6 +500,28 @@ cr.define('settings_people_page_quick_unlock', function() {
         assertDeepEquals(['PIN'], quickUnlockPrivateApi.activeModes);
         assertDeepEquals(['1111'], quickUnlockPrivateApi.credentials);
       });
+
+      test('TestContinueButtonState', function() {
+        pinKeyboard.value = '1111';
+        MockInteractions.tap(continueButton);
+
+        // Verify the button is disabled when we first enter the confirm step,
+        // since the PIN value is empty.
+        assertEquals('', pinKeyboard.value);
+        assertTrue(continueButton.disabled);
+
+        // Verify the button is enabled after we enter one digit.
+        pinKeyboard.value = '1';
+        assertFalse(continueButton.disabled);
+
+        // Verify the button is disabled after we try to submit a wrong PIN.
+        MockInteractions.tap(continueButton);
+        assertTrue(continueButton.disabled);
+
+        // Verify the button is enabled after we enter one digit again.
+        pinKeyboard.value = '11';
+        assertFalse(continueButton.disabled);
+      });
     });
   }