[iOS][Alert] Animate layout when keyboard (dis)appears

Animates the move of the alert with the new safe areas when the keyboard
appears. This animations has the same curve and duration of the keyboard
one.

R=kkhorimoto@chromium.org

Bug: 959737, 951300
Change-Id: Ie447fc5a76744f954fe57c4aa176edb4be0e07fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611820Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Auto-Submit: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666193}

ios/chrome/browser/ui/alert_view_controller/alert_view_controller.mm

@@ -64,6 +64,10 @@ constexpr int kButtonTextDefaultColor = 0x0579ff;
 constexpr int kButtonTextDestructiveColor = 0xdf322f;
 constexpr int kTextfieldBackgroundColor = 0xf7f7f7;
 
+// This is how many bits UIViewAnimationCurve needs to be shifted to be in
+// UIViewAnimationOptions format. Must match the one in UIView.h.
+constexpr NSUInteger kUIViewAnimationCurveToOptionsShift = 16;
+
 }  // namespace
 
 @interface AlertViewController () <UITextFieldDelegate,
@@ -464,6 +468,7 @@ constexpr int kTextfieldBackgroundColor = 0xf7f7f7;
   if (additionalBottomInset > 0) {
     self.additionalSafeAreaInsets =
         UIEdgeInsetsMake(0, 0, additionalBottomInset, 0);
+    [self animateLayoutFromKeyboardNotification:notification];
   }
 
   self.tapRecognizer.enabled = YES;
@@ -472,11 +477,31 @@ constexpr int kTextfieldBackgroundColor = 0xf7f7f7;
 
 - (void)handleKeyboardWillHide:(NSNotification*)notification {
   self.additionalSafeAreaInsets = UIEdgeInsetsZero;
+  [self animateLayoutFromKeyboardNotification:notification];
 
   self.tapRecognizer.enabled = NO;
   self.swipeRecognizer.enabled = NO;
 }
 
+- (void)animateLayoutFromKeyboardNotification:(NSNotification*)notification {
+  double duration =
+      [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey]
+          doubleValue];
+  UIViewAnimationCurve animationCurve = static_cast<UIViewAnimationCurve>(
+      [notification.userInfo[UIKeyboardAnimationCurveUserInfoKey]
+          integerValue]);
+  UIViewAnimationOptions options = animationCurve
+                                   << kUIViewAnimationCurveToOptionsShift;
+
+  [UIView animateWithDuration:duration
+                        delay:0
+                      options:options
+                   animations:^{
+                     [self.view layoutIfNeeded];
+                   }
+                   completion:nil];
+}
+
 - (void)didSelectActionForButton:(UIButton*)button {
   AlertAction* action = self.buttonAlertActionsDictionary[@(button.tag)];
   if (action.handler) {