[ios Mojo] Enabled Mojo WebUI by default.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index b85c68c996271e9bb2a097674c9f93a007c41f36..de95332ba9ecf795258d257f957b3394ee8447cb 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -1014,7 +1014,6 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
 @synthesize usePlaceholderOverlay = _usePlaceholderOverlay;
 @synthesize loadPhase = _loadPhase;
 @synthesize shouldSuppressDialogs = _shouldSuppressDialogs;
-@synthesize useMojoForWebUI = _useMojoForWebUI;
 
 - (instancetype)initWithWebState:(WebStateImpl*)webState {
   self = [super init];
@@ -4880,8 +4879,7 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
                         completionHandler:
                             (void (^)(NSString* result))completionHandler {
   GURL origin(web::GURLOriginWithWKSecurityOrigin(frame.securityOrigin));
-  if (self.useMojoForWebUI && web::GetWebClient()->IsAppSpecificURL(origin) &&
-      _webUIManager) {
+  if (web::GetWebClient()->IsAppSpecificURL(origin) && _webUIManager) {
     std::string mojoResponse =
         self.mojoFacade->HandleMojoMessage(base::SysNSStringToUTF8(prompt));
     completionHandler(base::SysUTF8ToNSString(mojoResponse));