Add pause/resume functionality to precache

components/precache/core/precache_database.h

Index: components/precache/core/precache_database.h
diff --git a/components/precache/core/precache_database.h b/components/precache/core/precache_database.h
index 94d045107b83c744dae7d00bf50e5dcdcedd826b..aaea1ca9bbc005fec56820e787c0038a8b80df3e 100644
--- a/components/precache/core/precache_database.h
+++ b/components/precache/core/precache_database.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <list>
 #include <memory>
 #include <string>
 #include <vector>
@@ -14,8 +15,11 @@
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
+#include "components/precache/core/precache_fetcher.h"
+#include "components/precache/core/precache_session_table.h"
 #include "components/precache/core/precache_url_table.h"
 
 class GURL;
@@ -31,6 +35,8 @@ class Connection;
 
 namespace precache {
 
+class PrecacheUnfinishedWork;
+
 // Class that tracks information related to precaching. This class may be
 // constructed on any thread, but all calls to, and destruction of this class
 // must be done on the the DB thread.
@@ -71,6 +77,19 @@ class PrecacheDatabase {
                             int host_rank,
                             bool is_connection_cellular);
 
+  // Gets the state required to continue a precache session.
+  std::unique_ptr<PrecacheUnfinishedWork> GetUnfinishedWork();
+
+  // Stores the state required to continue a precache session so that the
+  // session can be resumed later.
+  void SaveUnfinishedWork(
+      std::unique_ptr<PrecacheUnfinishedWork> unfinished_work);
+
+  // Deletes unfinished work from the database.
+  void DeleteUnfinishedWork();
+
+  base::WeakPtr<PrecacheDatabase> GetWeakPtr();
+
  private:
   friend class PrecacheDatabaseTest;
 
@@ -97,6 +116,10 @@ class PrecacheDatabase {
   // then this table will not be up to date until the next call to Flush().
   PrecacheURLTable precache_url_table_;
 
+  // Table that persists state related to a precache session, including
+  // unfinished work to be done.
+  PrecacheSessionTable precache_session_table_;
+
   // A vector of write operations to be run on the database.
   std::vector<base::Closure> buffered_writes_;