Reland "Make showcase home screen not translucent."

This relands "Make showcase home screen not translucent.".

Original change's description:
> Make showcase home screen not translucent.
>
> EarlGrey 1.10.1 has a bug that the scrollToTop action hangs
> indefinitely if the UITableView's navigation bar is translucent. Given
> that it makes no difference whether the view is translucent or not,
> this CL makes it not translucent to unblock rolling EarlGrey to 1.10.

Bug: 747116
Change-Id: I9c3af1633aac27439734925c142f8a684eeb9658
Reviewed-on: https://chromium-review.googlesource.com/580341Reviewed-by: Ed Chin <edchin@chromium.org>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488718}

ios/showcase/core/showcase_view_controller.mm

@@ -68,6 +68,7 @@ NSString* const kUseCaseKey = @"useCase";
   self.searchController.searchResultsUpdater = self;
   self.searchController.dimsBackgroundDuringPresentation = NO;
   self.tableView.tableHeaderView = self.searchController.searchBar;
+  self.navigationController.navigationBar.translucent = NO;
 
   // Presentation of searchController will walk up the view controller hierarchy
   // until it finds the root view controller or one that defines a presentation

ios/showcase/payments/sc_payments_editor_egtest.mm

@@ -316,8 +316,14 @@ id<GREYMatcher> UIAlertViewMessageForDelegateCallWithArgument(
 
   // The standard keyboard does not display for the province field. Instead, tap
   // the address textfield.
-  [[EarlGrey
-      selectElementWithMatcher:grey_accessibilityID(@"Address_textField")]
+  id<GREYMatcher> matcher =
+      grey_allOf(grey_accessibilityID(@"Address_textField"),
+                 grey_interactable(), grey_sufficientlyVisible(), nil);
+  [[[EarlGrey selectElementWithMatcher:matcher]
+         usingSearchAction:grey_scrollInDirection(kGREYDirectionDown, 50)
+      onElementWithMatcher:
+          grey_accessibilityID(
+              @"kPaymentRequestEditCollectionViewAccessibilityID")]
       performAction:grey_tap()];
 
   // Assert the address textfield is focused.

ios/showcase/tools_menu/sc_tools_coordinator.mm

@@ -53,10 +53,6 @@
   // The Overflow controls will only be displayed on CompactWidth SizeClasses.
   [viewController setDisplayOverflowControls:YES];
 
-  // Since the close MenuButton is always located on the top right corner,
-  // set the navigation translucency to NO so it doesn't cover the button.
-  self.baseViewController.navigationBar.translucent = NO;
-
   [self.baseViewController pushViewController:viewController animated:YES];
 }