predictors: Add the request priority to the reource_prefetch_predictor DB.

chrome/browser/predictors/resource_prefetch_predictor_tables.h

Index: chrome/browser/predictors/resource_prefetch_predictor_tables.h
diff --git a/chrome/browser/predictors/resource_prefetch_predictor_tables.h b/chrome/browser/predictors/resource_prefetch_predictor_tables.h
index 18c9473a72ff3f2e7d8037073e3a9aa9ea8ccd43..073df33e01f3b9346e4695eea59732a5368eee70 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor_tables.h
+++ b/chrome/browser/predictors/resource_prefetch_predictor_tables.h
@@ -16,6 +16,7 @@
 #include "chrome/browser/predictors/predictor_table_base.h"
 #include "chrome/browser/predictors/resource_prefetch_common.h"
 #include "content/public/common/resource_type.h"
+#include "net/base/request_priority.h"
 #include "url/gurl.h"
 
 namespace sql {
@@ -46,7 +47,8 @@ class ResourcePrefetchPredictorTables : public PredictorTableBase {
                 int number_of_hits,
                 int number_of_misses,
                 int consecutive_misses,
-                double average_position);
+                double average_position,
+                net::RequestPriority priority);
     void UpdateScore();
     bool operator==(const ResourceRow& rhs) const;
 
@@ -61,6 +63,7 @@ class ResourcePrefetchPredictorTables : public PredictorTableBase {
     size_t number_of_misses;
     size_t consecutive_misses;
     double average_position;
+    net::RequestPriority priority;
 
     // Not stored.
     float score;
@@ -142,6 +145,8 @@ class ResourcePrefetchPredictorTables : public PredictorTableBase {
   void CreateTableIfNonExistent() override;
   void LogDatabaseStats() override;
 
+  bool DropTablesIfOutdated(sql::Connection* db);
+
   // Helpers to return Statements for cached Statements. The caller must take
   // ownership of the return Statements.
   sql::Statement* GetUrlResourceDeleteStatement();