[iOS][MF] Fixes the size of the popover for passwords

Reduces the estimated size of the row to the minimum, so it is correctly
calculated on |contentSize|.
Starts the view controller with a more appropiate size for the popover.

Bug: 912515
Change-Id: If7c2dc4a0ab2a6df445fdac2c5fc21453927a71c
Reviewed-on: https://chromium-review.googlesource.com/c/1371873
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615855}

ios/chrome/browser/ui/autofill/manual_fill/fallback_coordinator.mm

@@ -68,7 +68,7 @@ initWithBaseViewController:(UIViewController*)viewController
   popoverPresentationController.sourceView = button;
   popoverPresentationController.sourceRect = button.bounds;
   popoverPresentationController.permittedArrowDirections =
-      UIPopoverArrowDirectionUp | UIMenuControllerArrowDown;
+      UIPopoverArrowDirectionUp | UIPopoverArrowDirectionDown;
   popoverPresentationController.delegate = self;
   popoverPresentationController.backgroundColor = UIColor.whiteColor;
 }

ios/chrome/browser/ui/autofill/manual_fill/fallback_view_controller.mm

@@ -24,10 +24,14 @@ typedef NS_ENUM(NSInteger, SectionIdentifier) {
 namespace {
 
 // This is the width used for |self.preferredContentSize|.
-constexpr float PopoverPreferredWidth = 320;
+constexpr CGFloat PopoverPreferredWidth = 320;
 
 // This is the maximum height used for |self.preferredContentSize|.
-constexpr float PopoverMaxHeight = 360;
+constexpr CGFloat PopoverMaxHeight = 360;
+
+// This is the height used for |self.preferredContentSize| when showing the
+// loading indicator on iPad.
+constexpr CGFloat PopoverLoadingHeight = 185.5;
 
 }  // namespace
 
@@ -61,11 +65,15 @@ constexpr float PopoverMaxHeight = 360;
   self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
   self.tableView.sectionHeaderHeight = 0;
   self.tableView.sectionFooterHeight = 20.0;
-  self.tableView.estimatedRowHeight = 200;
+  self.tableView.estimatedRowHeight = 1;
   self.tableView.separatorInset = UIEdgeInsetsMake(0, 0, 0, 0);
   self.tableView.allowsSelection = NO;
   self.definesPresentationContext = YES;
   if (!self.tableViewModel) {
+    if (IsIPadIdiom()) {
+      self.preferredContentSize = CGSizeMake(
+          PopoverPreferredWidth, AlignValueToPixel(PopoverLoadingHeight));
+    }
     [self startLoadingIndicatorWithLoadingMessage:@""];
   }
 }