Adding ChromeIdentity in ShowSigninCommand.

ios/chrome/browser/ui/commands/show_signin_command.mm

Index: ios/chrome/browser/ui/commands/show_signin_command.mm
diff --git a/ios/chrome/browser/ui/commands/show_signin_command.mm b/ios/chrome/browser/ui/commands/show_signin_command.mm
index b71ec1e1b404501df21d8ba36ff6c8ec040c556f..c0a6973d1796a930eb7e6d2a035bad9e6009eefb 100644
--- a/ios/chrome/browser/ui/commands/show_signin_command.mm
+++ b/ios/chrome/browser/ui/commands/show_signin_command.mm
@@ -14,6 +14,7 @@
 @implementation ShowSigninCommand
 
 @synthesize operation = _operation;
+@synthesize identity = _identity;
 @synthesize accessPoint = _accessPoint;
 @synthesize promoAction = _promoAction;
 @synthesize callback = _callback;
@@ -24,12 +25,15 @@
 }
 
 - (instancetype)initWithOperation:(AuthenticationOperation)operation
+                         identity:(ChromeIdentity*)identity
                       accessPoint:(signin_metrics::AccessPoint)accessPoint
                       promoAction:(signin_metrics::PromoAction)promoAction
                          callback:
                              (ShowSigninCommandCompletionCallback)callback {
   if ((self = [super initWithTag:IDC_SHOW_SIGNIN_IOS])) {
+    DCHECK(operation != AUTHENTICATION_OPERATION_SIGNIN && identity != nil);

[sdefresne, 2017/05/17 12:45:55]

I think this is incorrect as it will fail if operation ==
AUTHENTICATION_OPERATION_SIGNIN and identity == nil which is supported. I think
you want "operation != AUTHENTICATION_OPERATION_SIGNIN implies identity == nil".
This can be "A => B" can be encoded as "(not A) or B" so, I think the correct
DCHECK is:

  DCHECK(operation == AUTHENTICATION_OPERATION_SIGNIN || identity == nil);

[jlebel, 2017/05/17 13:11:06]

Done.

     _operation = operation;
+    _identity = identity;
     _accessPoint = accessPoint;
     _promoAction = promoAction;
     _callback = [callback copy];
@@ -41,6 +45,7 @@
                       accessPoint:(signin_metrics::AccessPoint)accessPoint
                       promoAction:(signin_metrics::PromoAction)promoAction {
   return [self initWithOperation:operation
+                        identity:nil
                      accessPoint:accessPoint
                      promoAction:promoAction
                         callback:nil];