Add pause/resume functionality to precache

components/precache/core/precache_session_tables.h

Index: components/precache/core/precache_session_tables.h
diff --git a/components/precache/core/precache_session_tables.h b/components/precache/core/precache_session_tables.h
new file mode 100644
index 0000000000000000000000000000000000000000..31e77c190e95decba19637f7050f9fd38c3ab751
--- /dev/null
+++ b/components/precache/core/precache_session_tables.h
@@ -0,0 +1,104 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PRECACHE_CORE_PRECACHE_SESSION_TABLES_H_
+#define COMPONENTS_PRECACHE_CORE_PRECACHE_SESSION_TABLES_H_
+
+#include <list>
+#include <map>
+
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "url/gurl.h"
+
+namespace base {
+class TimeTicks;
+}
+
+namespace sql {
+class Connection;
+}
+
+namespace precache {
+
+enum URLType {
+  MANIFEST = 1,
+  RESOURCE = 2
+};
+
+// Denotes the type of statistics that is recorded.
+enum StatType {

[sclittle, 2016/05/10 00:01:27]

Instead of using a Type enum, could you either use a protobuf (if you're worried
about easily adding new stats in the future) or just create a column for each of
these?

You could probably even just make the entire UnfinishedWork a protobuf if you
really wanted, and just serialize that to a string when saving it. Then this
whole PrecacheSessionTables could be replaced with just a single table with a
single row of the serialized proto.

[bengr, 2016/05/19 01:25:44]

Done.

+  // The sum total of all bytes in precache responses.
+  TOTAL_RESPONSE_BYTES = 0,
+
+  // The total precache response bytes retrieved over the network.
+  NETWORK_RESPONSE_BYTES = 1,
+
+  // The initial number of manifest URLs to fetch.
+  NUM_MANIFEST_URLS_TO_FETCH = 2,
+
+  // The initial start time of the precache session, before any interruptions.
+  START_TIME = 3
+};
+
+class PrecacheSessionTables {
+ public:
+  PrecacheSessionTables();
+  virtual ~PrecacheSessionTables();
+
+  // Initialize the precache task URL table for use with the specified database
+  // connection. The caller keeps ownership of |db|, and |db| must not be null.
+  // Init must be called before any other methods.
+  bool Init(sql::Connection* db);
+
+  // Get the manifest and resource URLs that still need to be fetched.
+  void GetURLs(std::list<GURL>* manifests,
+               std::list<GURL>* resources);
+
+  // Get statistics from the last time the precache session state was stored.
+  void GetStatistics(int64_t* total_response_bytes,
+                     int64_t* network_response_bytes,
+                     int64_t* num_manifest_urls_to_fetch,
+                     base::TimeTicks* start_time);
+
+  // Store outstanding manifest and resource URLs for the current precache
+  // session.
+  void StoreURLs(const std::list<GURL>& manifests,
+                 const std::list<GURL>& resources);
+
+  // Store statistics for the current precache session.
+  void StoreStatistics(int64_t total_response_bytes,
+                       int64_t network_response_bytes,
+                       int64_t num_manifest_urls_to_fetch,
+                       const base::TimeTicks& start_time);
+
+  // Remove all manifest and resource URLs from the database.
+  void ClearURLs();
+
+  // Remove all statistics from the database.
+  void ClearStatistics();
+
+ private:
+  // Adds a URL to the table. A |MANIFEST| type
+  // is a url of a manifest to be fetched; A |RESOURCE| type is a url of a
+  // page resource to be fetched. Replaces the row if one already exists.
+  void StoreURL(const GURL& url, URLType type);
+
+  // Adds a statistic of type |StatType| with a corresponding value. Overwrites
+  // the value if it already exists.
+  void StoreStatistic(StatType type, int64_t value);
+
+  // Deletes the row from the table that has the given URL, if it exists.
+  void DeleteURL(const GURL& url);
+
+  bool CreateTablesIfNonExistent();
+
+  // Non-owned pointer.
+  sql::Connection* db_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrecacheSessionTables);
+};
+
+}  // namespace precache
+#endif  // COMPONENTS_PRECACHE_CORE_PRECACHE_SESSION_TABLES_H_