Fix testSearchPasswords failure on small screens.

After migrated to ChromeTableView, PasswordsTableViewController
(use to be SavePasswordsCollectionViewController) displays less items in
one screen, and testSearchPasswords has to scroll down to find all items
which will hide the search bar. Then it will fail when trying to tap on
search bar. This CL makes it scroll to top first and then tap the search
bar.

Change-Id: I08327f99043b26b426a0f41fdb32e578e93c3b74
Reviewed-on: https://chromium-review.googlesource.com/c/1373827Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615977}

ios/chrome/browser/ui/settings/passwords_settings_egtest.mm

@@ -1601,6 +1601,9 @@ PasswordForm CreateSampleFormWithIndex(int index) {
   [GetInteractionForPasswordEntry(@"exclude2.com")
       assertWithMatcher:grey_notNil()];
 
+  [[EarlGrey
+      selectElementWithMatcher:grey_accessibilityID(kPasswordsTableViewId)]
+      performAction:grey_scrollToContentEdge(kGREYContentEdgeTop)];
   [[EarlGrey selectElementWithMatcher:SearchTextField()]
       performAction:grey_typeText(@"2")];