[iOS] Instantiate the toolbar out of fullscreen

This CL sets the fullscreen progress of the toolbar to 1 (meaning
fullscreen isn't enabled) when the toolbar view is created.
It allows the constraints to be correctly positioned the first time
the toolbar is shown.

Bug: 895870
Change-Id: I481342521cd1b396f4d00c9f6dcc2a8a3f4cb1eb
Reviewed-on: https://chromium-review.googlesource.com/c/1297975
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602435}

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

@@ -95,6 +95,8 @@
 - (void)loadView {
   DCHECK(self.buttonFactory);
 
+  self.previousFullscreenProgress = 1;
+
   self.view =
       [[PrimaryToolbarView alloc] initWithButtonFactory:self.buttonFactory];