[iOS] Disable URL clipping on iOS 12.

Disable URL clipping in the omnibox on iOS 12. The omnibox will just
show an ellipsis in the end if the URL is too long. This only affects
pre-UI Refresh and is considered a temporary workaround.

Bug: 860790
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I879c24f8ba7602a9b7bb5816529d330b3e840b2c
Reviewed-on: https://chromium-review.googlesource.com/1158566Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579792}

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

@@ -4,6 +4,7 @@
 
 #import "ios/chrome/browser/ui/omnibox/clipping_textfield_container.h"
 
+#include "base/ios/ios_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/omnibox/browser/autocomplete_input.h"
 #include "ios/chrome/browser/autocomplete/autocomplete_scheme_classifier_impl.h"
@@ -68,6 +69,14 @@
 }
 
 - (void)startClipping {
+  // TODO(crbug.com/860790) : reenable this.
+  if (base::ios::IsRunningOnIOS12OrLater()) {
+    // Clipping is disabled on iOS 12 due to a bug with UITextField not being
+    // rendered when the backing layer is large (approx. 915 characters with
+    // current font).
+    return;
+  }
+
   self.clipping = YES;
   [self applyClipping];
   [self setNeedsLayout];