fix(element): return not present when an element disappears

lib/element.js

@@ -353,7 +353,23 @@ ElementArrayFinder.prototype.toElementFinder_ = function() {
  */
 ElementArrayFinder.prototype.count = function() {
   return this.getWebElements().then(function(arr) {
-    return arr.length;
+    var list = arr.map(function(webElem) {
+      // Calling any method forces a staleness check
+      return webElem.isEnabled().then(function() {
+        return 1; // is present
+      }, function(err) {
+        if (err.code == webdriver.error.ErrorCode.STALE_ELEMENT_REFERENCE) {
+          return 0; // not present
+        } else {
+          throw err;
+        }
+      });
+    });
+    return webdriver.promise.all(list).then(function(presenceArr) {
+      return presenceArr.reduce(function(acc, isPresent) {
+        return acc + isPresent;
+      }, 0);
+    });
   }, function(err) {
     if (err.code == webdriver.error.ErrorCode.NO_SUCH_ELEMENT) {
       return 0;

spec/basic/elements_spec.js

@@ -364,6 +364,17 @@ describe('ElementArrayFinder', function() {
     expect(element.all(by.binding('doesnotexist')).count()).toEqual(0);
   });
 
+  it('should return not present when an element disappears within an array', 
+      function() {
+    browser.get('index.html#/form');
+    element.all(by.model('color')).then(function(elements) {
+      var disappearingElem = elements[0];
+      expect(disappearingElem.isPresent()).toBeTruthy();
+      browser.get('index.html#/bindings');
+      expect(disappearingElem.isPresent()).toBeFalsy();
+    });
+  });
+
   it('should get an element from an array', function() {
     var colorList = element.all(by.model('color'));