Fix inline autocomplete highlight color.

Avoids caching the inline autocomplete color in UI Refresh, and uses
_displayedTintColor instead of self.tintColor (which can be transparent
when the textfield is hidden behind inline autocomplete or preedit).

Bug: 865497
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I358cd0b10694271d4d0514b3dfe9b7415c1c9106
Reviewed-on: https://chromium-review.googlesource.com/1152985Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579736}

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

@@ -985,18 +985,17 @@ NSString* const kOmniboxFadeAnimationKey = @"OmniboxFadeAnimation";
 }
 
 - (UIColor*)selectedTextBackgroundColor {
-  if (!_selectedTextBackgroundColor) {
-    if (IsUIRefreshPhase1Enabled()) {
-      _selectedTextBackgroundColor =
-          [self.tintColor colorWithAlphaComponent:0.2];
-    } else {
+  if (IsUIRefreshPhase1Enabled()) {
+    return [_displayedTintColor colorWithAlphaComponent:0.2];
+  } else {
+    if (!_selectedTextBackgroundColor) {
       _selectedTextBackgroundColor = [UIColor colorWithRed:204.0 / 255
                                                      green:221.0 / 255
                                                       blue:237.0 / 255
                                                      alpha:1.0];
     }
+    return _selectedTextBackgroundColor;
   }
-  return _selectedTextBackgroundColor;
 }
 
 - (BOOL)isColorHidden:(UIColor*)color {