Change Lo-Fi bool to bitmask to support multiple Previews types

chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h

Index: chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h
diff --git a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h
index ca97f1c6676d9b7ed184864621714885116b958b..9511eee452961fe7096a599068a09d711b766ce9 100644
--- a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h
+++ b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.h
@@ -15,6 +15,7 @@
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
 #include "content/public/browser/resource_dispatcher_host_delegate.h"
+#include "content/public/common/previews_state.h"
 #include "extensions/features/features.h"
 
 class DownloadRequestLimiter;
@@ -83,7 +84,8 @@ class ChromeResourceDispatcherHostDelegate
                            content::ResourceContext* resource_context,
                            content::ResourceResponse* response) override;
   void RequestComplete(net::URLRequest* url_request) override;
-  bool ShouldEnableLoFiMode(
+  // Returns a bitmask of potentially several Previews optimizations.
+  content::PreviewsState GetPreviewsState(
       const net::URLRequest& url_request,
       content::ResourceContext* resource_context) override;
   content::NavigationData* GetNavigationData(