Revert "[iOS] Change omnibox pre-edit exiting behavior."

This reverts commit 05d76942.

This change was introduced to work around an iOS 13 bug which is now
fixed. Therefore it can be reverted.

Bug: 988431, 875918, 873544
Change-Id: If0d0ecb7a3f22097f662e01a35d631b2a997be9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1807251
Auto-Submit: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Robbie Gibson <rkgibson@google.com>
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/master@{#697597}

ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm

@@ -438,24 +438,13 @@ bool OmniboxViewIOS::OnWillChange(NSRange range, NSString* new_text) {
     [field_ setClearingPreEditText:YES];
 
     // Exit the pre-editing state in OnWillChange() instead of OnDidChange(), as
-    // that allows IME to continue working.
+    // that allows IME to continue working.  The following code selects the text
+    // as if the pre-edit fake selection was real.
     [field_ exitPreEditState];
 
-    if (@available(iOS 13, *)) {
-      // Exit pre-edit completely by setting the text to an empty string.
-      // On iOS 13, swiping keyboard acquires a lock that UITextField attempts
-      // to acquire when setSelectedTextRange: is called, causing a deadlock.
-      // Therefore this workaround is introduced. This probably introduces small
-      // issues with third-party keyboards, like crbug.com/875918 and
-      // crbug.com/873544. See crbug.com/988431 for more context.
-      [field_ setText:@""];
-    } else {
-      // The following code selects the text
-      // as if the pre-edit fake selection was real.
-      field_.selectedTextRange =
-          [field_ textRangeFromPosition:field_.beginningOfDocument
-                             toPosition:field_.endOfDocument];
-    }
+    field_.selectedTextRange =
+        [field_ textRangeFromPosition:field_.beginningOfDocument
+                           toPosition:field_.endOfDocument];
 
     // Reset |range| to be of zero-length at location zero, as the field will be
     // now cleared.