predictors: Add origin learning.

chrome/browser/predictors/resource_prefetch_predictor.proto

Index: chrome/browser/predictors/resource_prefetch_predictor.proto
diff --git a/chrome/browser/predictors/resource_prefetch_predictor.proto b/chrome/browser/predictors/resource_prefetch_predictor.proto
index 40e3681d08704999ec6a3e18d544c8aea5d0a1a0..7a6d8d7fc2cc0f7c2eaf6294293c9fd947ebfb0c 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.proto
+++ b/chrome/browser/predictors/resource_prefetch_predictor.proto
@@ -83,3 +83,21 @@ message RedirectData {
   optional uint64 last_visit_time = 2;
   repeated RedirectStat redirect_endpoints = 3;
 }
+
+// Historical data for a single origin accessed from a host.
+message OriginStat {
+  optional string origin = 1;
+  optional uint32 number_of_hits = 2;
+  optional uint32 number_of_misses = 3;
+  optional uint32 consecutive_misses = 4;
+  optional double average_position = 5;
+  optional bool always_access_network = 6;
+  optional bool accessed_network = 7;
+}
+
+// Collection of origins accessed from a host.
+message OriginData {
+  optional string host = 1;
+  optional uint64 last_visit_time = 2;
+  repeated OriginStat origins = 3;
+}