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..54fcbb992c9e60d1d908c279754dbfeaf8a80ea9 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.proto
+++ b/chrome/browser/predictors/resource_prefetch_predictor.proto
@@ -83,3 +83,19 @@ message RedirectData {
   optional uint64 last_visit_time = 2;
   repeated RedirectStat redirect_endpoints = 3;
 }
+
+message OriginData {

[alexilin, 2017/04/10 14:58:28]

Some comments to the messages?

[Benoit L, 2017/04/11 09:04:05]

Done.

+  message OriginStat {

[alexilin, 2017/04/10 14:58:28]

It could be more convenient to not nest messages. Nesting only causes
unnecessary namespaces pain.
(I'd move RedirectStat outside of RedirectData if I could make it painless)

[Benoit L, 2017/04/11 09:04:05]

Done.
The changes were surprisingly minimal though (just removing two typedefs).

+    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;
+  }
+
+  optional string host = 1;
+  optional uint64 last_visit_time = 2;
+  repeated OriginStat origins = 3;
+}