Correct iOS build for latest Xcode beta.

ios/chrome/browser/xcallback_parameters.mm

Index: ios/chrome/browser/xcallback_parameters.mm
diff --git a/ios/chrome/browser/xcallback_parameters.mm b/ios/chrome/browser/xcallback_parameters.mm
index 0d55d38b85334d24c891bbd5daff072a78f7c8fa..c9f5370a7e46c1add40f6803bbfcd8c6a9325139 100644
--- a/ios/chrome/browser/xcallback_parameters.mm
+++ b/ios/chrome/browser/xcallback_parameters.mm
@@ -4,6 +4,7 @@
 
 #import "ios/chrome/browser/xcallback_parameters.h"
 
+#include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 
@@ -27,6 +28,11 @@ NSString* const kCreateNewTabKey = @"createNewTab";
 @synthesize successURL = _successURL;
 @synthesize createNewTab = _createNewTab;
 
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
 - (instancetype)initWithSourceAppId:(NSString*)sourceAppId
                       sourceAppName:(NSString*)sourceAppName
                          successURL:(const GURL&)successURL