Add support to previews/ for Server LoFi and LitePages

components/previews/core/previews_decider.h

Index: components/previews/core/previews_decider.h
diff --git a/components/previews/core/previews_decider.h b/components/previews/core/previews_decider.h
index f293c87c1ad0f621e85cf0756f6872cf0c2f6c60..2ba7541d147f1a0f0b3be05cc2f707e4bc87abd5 100644
--- a/components/previews/core/previews_decider.h
+++ b/components/previews/core/previews_decider.h
@@ -7,6 +7,8 @@
 
 #include "components/previews/core/previews_experiments.h"
 
+#include "net/nqe/effective_connection_type.h"
+
 namespace net {
 class URLRequest;
 }
@@ -15,7 +17,17 @@ namespace previews {
 
 class PreviewsDecider {
  public:
-  // Whether |request| is allowed to show a preview of |type|.
+  // Whether |request| is allowed to show a preview of |type|. Previews that do
+  // not supply a network quality in
+  // GetEffectiveConnectionTypeThresholdForPreviewsType() should check the
+  // network quality before calling ShouldAllowPreview.
+  virtual bool ShouldAllowPreview(
+      const net::URLRequest& request,
+      PreviewsType type,
+      net::EffectiveConnectionType effective_connection_type_threshold)
+      const = 0;
+
+  // Same as above, but uses the previews default EffectiveConnectionType.
   virtual bool ShouldAllowPreview(const net::URLRequest& request,
                                   PreviewsType type) const = 0;