Handle empty timezone on in-session set date time dialog

Bug: 988107
Change-Id: Ia9c12a9342342bc080f73ddbe5ba86531b29997e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724696Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Commit-Queue: Henrique Grandinetti <hgrandinetti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683159}

chrome/browser/resources/chromeos/set_time_dialog/set_time_dialog.js

@@ -267,11 +267,15 @@ Polymer({
   applyTime_: function() {
     const now = this.getInputTime_();
 
-    // Add timezone offset to get real time.
-    const timezoneDelta = getTimezoneDelta(
-        /** @type {string} */ (loadTimeData.getValue('currentTimezoneId')),
-        this.selectedTimezone_);
-    now.setMilliseconds(now.getMilliseconds() + timezoneDelta);
+    if (this.isTimezoneVisible_) {
+      // Add timezone offset to get real time. This is only necessary when the
+      // timezone was updated, which is only possible when the dropdown is
+      // visible.
+      const timezoneDelta = getTimezoneDelta(
+          /** @type {string} */ (loadTimeData.getValue('currentTimezoneId')),
+          this.selectedTimezone_);
+      now.setMilliseconds(now.getMilliseconds() + timezoneDelta);
+    }
 
     const seconds = Math.floor(now / 1000);
     this.browserProxy_.setTimeInSeconds(seconds);

chrome/test/data/webui/set_time_dialog_browsertest.js

@@ -187,6 +187,38 @@ TEST_F('SetTimeDialogBrowserTest', 'All', function() {
             assertGT(timeInSeconds, todaySeconds);
           });
     });
+
+    suite('NullTimezone', () => {
+      suiteSetup(() => {
+        loadTimeData.overrideValues({
+          currentTimezoneId: '',
+          timezoneList: [],
+        });
+      });
+
+      test('SetDateNullTimezone', () => {
+        const dateInput = setTimeElement.$$('#dateInput');
+        assertTrue(!!dateInput);
+
+        assertEquals(null, setTimeElement.$$('#timezoneSelect'));
+
+        // Simulate the user changing the date picker backward by one hour.
+        const today = dateInput.valueAsDate;
+        const nextWeek = new Date(today.getTime() - 60 * 60 * 1000);
+        dateInput.focus();
+        dateInput.valueAsDate = nextWeek;
+        setTimeElement.$$('#doneButton').click();
+
+        // Verify the page sends a request to move time backward.
+        return testBrowserProxy.whenCalled('setTimeInSeconds')
+            .then(timeInSeconds => {
+              const todaySeconds = today.getTime() / 1000;
+              // The exact value isn't important (it depends on the current
+              // time).
+              assertGT(todaySeconds, timeInSeconds);
+            });
+      });
+    });
   });
 
   mocha.run();