[iOS] Disable omnibox drag on iPhone

This CL disables dragging text out of the omnibox on iPhone because
there is nowhere to drag the text to.

Bug: 834778
Change-Id: Ic5c731b8c5400c40e7357c5ff25e5a8e45f3e544
Reviewed-on: https://chromium-review.googlesource.com/c/1363194Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/master@{#614314}

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

@@ -144,6 +144,11 @@ NSString* const kOmniboxFadeAnimationKey = @"OmniboxFadeAnimation";
 
     [self setSmartQuotesType:UITextSmartQuotesTypeNo];
 
+    // Disable drag on iPhone because there's nowhere to drag to
+    if (!IsIPadIdiom()) {
+      self.textDragInteraction.enabled = NO;
+    }
+
     // Sanity check:
     DCHECK([self conformsToProtocol:@protocol(UITextInput)]);