Add a way to send the resource percentage signal to the RC.

components/offline_pages/core/background/offliner.h

Index: components/offline_pages/core/background/offliner.h
diff --git a/components/offline_pages/core/background/offliner.h b/components/offline_pages/core/background/offliner.h
index c24aa46300745edaca26dcec929a82796cc605e7..7a4d96c37065a0e14b4f715f1afc90aa8a53ab92 100644
--- a/components/offline_pages/core/background/offliner.h
+++ b/components/offline_pages/core/background/offliner.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/callback.h"
+#include "components/offline_pages/core/background/resource_data_type.h"
 
 namespace offline_pages {
 
@@ -102,6 +103,12 @@ class Offliner {
   // offlining will be provided by |completion_callback|.
   virtual bool HandleTimeout(int64_t request_id) = 0;
 
+  // We are notified of a resource load starting or ending, we can use this
+  // for tracking loading signals.
+  virtual void ObserveResourceTracking(const ResourceDataType type,
+                                       int64_t started_count,
+                                       int64_t completed_count) = 0;
+
   // TODO(dougarnett): add policy support methods.
 };