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..a0e22022696a8aa56aba95db5464d2e19de734bf 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_tables.h"
 #include "components/precache/core/precache_url_table.h"
 
 class GURL;
@@ -31,6 +35,56 @@ class Connection;
 
 namespace precache {
 
+// Represents the precache work that is left over after a precache session
+// is interrupted.
+class UnfinishedWork : public base::RefCountedThreadSafe<UnfinishedWork> {

[sclittle, 2016/05/10 00:01:26]

See my comment in precache_fetcher.cc about passing this around as a
std::unique_ptr instead of refcounting.

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

Done.

+ public:
+  // Constructor used when saving unfinished work to storage.
+  // |manifest_urls_to_fetch| and |resource_urls_to_fetch| are the
+  // remaining manifest and resource URLs to fetch. |total_response_bytes|
+  // and |network_response_bytes| are counts of bytes receieved, the former
+  // including bytes received from local cache. |num_manifest_urls_to_fetch|
+  // is the initial number of manifest URLs that needed to be fetched. The
+  // |start_time_of_session| is the time the precache session began, before
+  // any interruptions.
+  UnfinishedWork(const std::list<GURL>& manifest_urls_to_fetch,
+                 const std::list<GURL>& resource_urls_to_fetch,
+                 int64_t total_response_bytes,
+                 int64_t network_response_bytes,
+                 int64_t num_manifest_urls_to_fetch,
+                 const base::TimeTicks& start_time_of_session);
+
+  // Constructor used when retrieving unfinished work from storage. No work
+  // saved before |earliest_start_time_of_session| will be retrieved.
+  explicit UnfinishedWork(
+      const base::TimeTicks& earliest_start_time_of_session);
+
+  // Manifest URLs remaining to be fetched.
+  std::list<GURL> manifests;

[sclittle, 2016/05/10 00:01:26]

If you just have publicly visible members, then could you change UnfinishedWork
to be a struct instead of a class? Otherwise, you should add getters and setters
for each.

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

Done.

+
+  // Resource URLs remaining to be fetched.
+  std::list<GURL> resources;
+
+  // Count of the total received bytes.
+  int64_t total_bytes;
+
+  // Count of the total received bytes over the network.
+  int64_t network_bytes;
+
+  // The total number of manifest URLs that the precache session started with.
+  int64_t num_manifest_urls;
+
+  // The original time the precache session started, not the time it resumed.
+  base::TimeTicks start_time;

[sclittle, 2016/05/10 00:01:26]

Should this be base::Time instead? I don't think it's safe to compare
base::TimeTicks values between different sessions, especially if the device was
rebooted or something.

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

Done.

+
+ private:
+  friend class base::RefCountedThreadSafe<UnfinishedWork>;
+
+  ~UnfinishedWork();
+
+  DISALLOW_COPY_AND_ASSIGN(UnfinishedWork);
+};
+
 // 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 +125,18 @@ class PrecacheDatabase {
                             int host_rank,
                             bool is_connection_cellular);
 
+  // Gets the state required to continue a precache session.
+  void GetUnfinishedWork(scoped_refptr<UnfinishedWork> unfinished_work);
+
+  // Stores the state required to continue a precache session so that the
+  // session can be resumed later.
+  void SaveUnfinishedWork(scoped_refptr<UnfinishedWork> unfinished_work);
+
+  // Clears all precache session state.
+  void ClearPrecacheSessionState();
+
+  base::WeakPtr<PrecacheDatabase> GetWeakPtr();
+
  private:
   friend class PrecacheDatabaseTest;
 
@@ -97,6 +163,10 @@ class PrecacheDatabase {
   // then this table will not be up to date until the next call to Flush().
   PrecacheURLTable precache_url_table_;
 
+  // Tables that persist the state required to pause and resume a precache
+  // session.
+  PrecacheSessionTables precache_session_tables_;
+
   // A vector of write operations to be run on the database.
   std::vector<base::Closure> buffered_writes_;