[ios] Fix omnibox baseWritingDirection and dismissal iOS11 bugs.

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

Index: ios/chrome/browser/ui/omnibox/omnibox_text_field_ios.mm
diff --git a/ios/chrome/browser/ui/omnibox/omnibox_text_field_ios.mm b/ios/chrome/browser/ui/omnibox/omnibox_text_field_ios.mm
index 1180cf6b75987b1c03cfa0e5866ef4cccc57d712..1d47dbd32c0bd51ca1c7b91908f24382e816bc1d 100644
--- a/ios/chrome/browser/ui/omnibox/omnibox_text_field_ios.mm
+++ b/ios/chrome/browser/ui/omnibox/omnibox_text_field_ios.mm
@@ -554,7 +554,7 @@ NSString* const kOmniboxFadeAnimationKey = @"OmniboxFadeAnimation";
     return;
   }
 
-  NSTextAlignment alignment = [self bestTextAlignment];
+  NSTextAlignment alignment = [self bestAlignmentForText:[self text]];

[rohitrao (ping after 24h), 2017/06/12 22:08:52]

Why is it ok to always use [self text] here?

Is this better or worse than updating this function to properly handle Natural
alignments?

   [self setTextAlignment:alignment];
   UITextWritingDirection writingDirection =
       alignment == NSTextAlignmentLeft ? UITextWritingDirectionLeftToRight