[ObjC ARC] Converts ios/chrome/browser/ui/omnibox:omnibox_internal to ARC.

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

Index: ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm
diff --git a/ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm b/ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm
index 47bf4aebde093f33a43e9ae01a3fd16b7527d748..8bdb0b031a9bc37c5fc94b75b94d2e774c735161 100644
--- a/ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm
+++ b/ios/chrome/browser/ui/omnibox/omnibox_view_ios.mm
@@ -37,6 +37,10 @@
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/image/image.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using base::UserMetricsAction;
 
 namespace {
@@ -182,7 +186,7 @@ OmniboxViewIOS::OmniboxViewIOS(OmniboxTextFieldIOS* field,
           controller,
           base::MakeUnique<ChromeOmniboxClientIOS>(controller, browser_state)),
       browser_state_(browser_state),
-      field_([field retain]),
+      field_(field),
       controller_(controller),
       preloader_(preloader),
       ignore_popup_updates_(false) {
@@ -636,8 +640,8 @@ void OmniboxViewIOS::WillPaste() {
 
 NSAttributedString* OmniboxViewIOS::ApplyTextAttributes(
     const base::string16& text) {
-  NSMutableAttributedString* as = [[[NSMutableAttributedString alloc]
-      initWithString:base::SysUTF16ToNSString(text)] autorelease];
+  NSMutableAttributedString* as = [[NSMutableAttributedString alloc]
+      initWithString:base::SysUTF16ToNSString(text)];
   url::Component scheme, host;
   AutocompleteInput::ParseForEmphasizeComponents(
       text, AutocompleteSchemeClassifierImpl(), &scheme, &host);