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..a3d663268235ac74f959ab71c3578740e5ae5fa9 100644
--- a/components/previews/core/previews_decider.h
+++ b/components/previews/core/previews_decider.h
@@ -15,7 +15,9 @@ 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 use the default network quality threhold should check the network

[tbansal1, 2017/05/02 21:49:31]

typo in threhold.

May be somehow refer to GetEffectiveConnectionTypeThresholdForPreviewsType() to
make it clear how the place of the code where previews  "use the default network
quality threshold".

[RyanSturm, 2017/05/02 22:57:19]

Done.

+  // quality before calling ShouldAllowPreview.
   virtual bool ShouldAllowPreview(const net::URLRequest& request,
                                   PreviewsType type) const = 0;