Change vertical alignment of the collapsed toolbar

This CL changes the vertical constraints of the collapsed toolbar to
have the location bar displayed in the middle of the collapsed toolbar
by changing the constraint to position its bottom anchor.

Bug: 836817
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I35ad32681a820b8480ecec76e825defc4c0aa2ef
Reviewed-on: https://chromium-review.googlesource.com/1107061
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568768}

ios/chrome/browser/ui/toolbar/adaptive/primary_toolbar_view_controller.mm

@@ -135,6 +135,8 @@
       (kAdaptiveToolbarHeight - 2 * kAdaptiveLocationBarVerticalMargin -
        kToolbarHeightFullscreen) *
           progress);
+  self.view.locationBarBottomConstraint.constant =
+      -AlignValueToPixel(kAdaptiveLocationBarVerticalMargin * progress);
   self.view.locationBarContainer.backgroundColor =
       [self.buttonFactory.toolbarConfiguration
           locationBarBackgroundColorWithVisibility:alphaValue];