fix(datepicker): fix bad valid date check and resize-on-open.

Closes #4270.

src/components/datepicker/datePicker.js

@@ -60,7 +60,9 @@
 
           // This pane will be detached from here and re-attached to the document body.
           '<div class="md-datepicker-calendar-pane md-whiteframe-z1">' +
-            '<div class="md-datepicker-input-mask"></div>' +
+            '<div class="md-datepicker-input-mask">' +
+              '<div class="md-datepicker-input-mask-opaque"></div>' +
+            '</div>' +
             '<div class="md-datepicker-calendar">' +
               '<md-calendar role="dialog" aria-label="{{::ctrl.dateLocale.msgCalendar}}" ' +
                   'ng-model="ctrl.date" ng-if="ctrl.isCalendarOpen"></md-calendar>' +
@@ -134,6 +136,12 @@
     /** @type {HTMLElement} Calendar icon button. */
     this.calendarButton = $element[0].querySelector('.md-datepicker-button');
 
+    /**
+     * Element covering everything but the input in the top of the floating calendar pane.
+     * @type {HTMLElement}
+     */
+    this.inputMask = $element[0].querySelector('.md-datepicker-input-mask-opaque');
+
     /** @final {!angular.JQLite} */
     this.$element = $element;
 
@@ -262,7 +270,7 @@
 
     Object.defineProperty(this, 'placeholder', {
       get: function() { return self.inputElement.placeholder; },
-      set: function(value) { self.inputElement.placeholder = value; }
+      set: function(value) { self.inputElement.placeholder = value || ''; }
     });
   };
 
@@ -313,6 +321,12 @@
     calendarPane.style.top = (elementRect.top - bodyRect.top) + 'px';
     document.body.appendChild(this.calendarPane);
 
+    // The top of the calendar pane is a transparent box that shows the text input underneath.
+    // Since the pane is flowing, though, the page underneath the pane *adjacent* to the input is
+    // also shown unless we cover it up. The inputMask does this by filling up the remaining space
+    // based on the width of the input.
+    this.inputMask.style.left = elementRect.width + 'px';
+
     // Add CSS class after one frame to trigger open animation.
     this.$$rAF(function() {
       calendarPane.classList.add('md-pane-open');

src/components/datepicker/datePicker.scss

@@ -3,6 +3,10 @@ $md-datepicker-button-gap: 12px;  // Space between the text input and the calend
 $md-datepicker-border-bottom-gap: 5px;  // Space between input and the grey underline.
 $md-datepicker-open-animation-duration: 0.2s;
 
+md-datepicker {
+  // Don't let linebreaks happen between the open icon-button and the input.
+  white-space: nowrap;
+}
 
 // The calendar icon button used to open the calendar pane.
 // Need absurd specificty to override md-button.md-icon-button.
@@ -62,12 +66,22 @@ $md-datepicker-open-animation-duration: 0.2s;
 .md-datepicker-input-mask {
   height: 40px;
   width: $md-calendar-width;
+  position: relative;
 
   background: transparent;
   pointer-events: none;
   cursor: text;
 }
 
+.md-datepicker-input-mask-opaque {
+  position: absolute;
+  right: 0;
+  left: 120px;
+  background: white;
+
+  height: 100%;
+}
+
 // The calendar portion of the floating pane (vs. the input mask).
 .md-datepicker-calendar {
   opacity: 0;
@@ -136,7 +150,6 @@ md-datepicker[disabled] {
 // Open state for all of the elements of the picker.
 .md-datepicker-open {
   .md-datepicker-input-container {
-    min-width: $md-calendar-width;
     margin-left: -$md-datepicker-button-gap;
     border: none;
   }

src/components/datepicker/datePicker.spec.js

@@ -45,6 +45,7 @@ describe('md-date-picker', function() {
     $timeout.flush();
 
     expect(controller.calendarPane.offsetHeight).toBeGreaterThan(0);
+    expect(controller.inputMask.style.left).toBe(controller.inputContainer.clientWidth + 'px');
 
     // Click off of the calendar.
     document.body.click();

src/components/datepicker/dateUtil.js

@@ -185,7 +185,7 @@
      * @return {boolean} Whether the date is a valid Date.
      */
     function isValidDate(date) {
-      return date !== null && date.getTime && !isNaN(date.getTime());
+      return date != null && date.getTime && !isNaN(date.getTime());
     }
 
     /**

src/components/datepicker/dateUtil.spec.js

@@ -303,4 +303,19 @@ describe('$$mdDateUtil', function() {
     expect(dayAtMidnight.getSeconds()).toBe(0);
     expect(dayAtMidnight.getMilliseconds()).toBe(0);
   });
+
+  it('should determine whether dates are valid', function() {
+    expect(dateUtil.isValidDate(null)).toBeFalsy();
+    expect(dateUtil.isValidDate(undefined)).toBeFalsy();
+    expect(dateUtil.isValidDate('')).toBeFalsy();
+    expect(dateUtil.isValidDate(0)).toBeFalsy();
+    expect(dateUtil.isValidDate(NaN)).toBeFalsy();
+    expect(dateUtil.isValidDate(123456789)).toBeFalsy();
+    expect(dateUtil.isValidDate('123456789')).toBeFalsy();
+    expect(dateUtil.isValidDate(new Date(''))).toBeFalsy();
+    expect(dateUtil.isValidDate(new Date('Banjo'))).toBeFalsy();
+    expect(dateUtil.isValidDate(new Date(NaN))).toBeFalsy();
+
+    expect(dateUtil.isValidDate(new Date())).toBe(true);
+  });
 });

src/components/input/demoBasicUsage/script.js

@@ -4,7 +4,6 @@ angular
     $scope.user = {
       title: 'Developer',
       email: 'ipsum@lorem.com',
-      submissionDate: new Date(),
       firstName: '',
       lastName: '' ,
       company: 'Google' ,