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..8554aa7624d110b09b9cd206f283de9b3829fe56 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"
 
@@ -41,6 +42,11 @@ NSString* const kCreateNewTabKey = @"createNewTab";
   return self;
 }
 
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
 - (NSString*)description {
   return [NSString stringWithFormat:@"SourceApp: %@ (%@)\nSuccessURL: %s\n",
                                     _sourceAppName.get(), _sourceAppId.get(),