add a download slices table into history download db

components/history/core/browser/download_database.h

Index: components/history/core/browser/download_database.h
diff --git a/components/history/core/browser/download_database.h b/components/history/core/browser/download_database.h
index 6388195eccf2b1b0f314fe86c21487ce10a6fd21..a869f48a941573bbae56bc74793bcca244ccb53b 100644
--- a/components/history/core/browser/download_database.h
+++ b/components/history/core/browser/download_database.h
@@ -14,6 +14,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/threading/platform_thread.h"
+#include "components/history/core/browser/download_job_info.h"

[sky, 2017/02/03 16:02:33]

Forward declare DownloadJobInfo?

[qinmin, 2017/02/04 00:06:56]

Done.

 #include "components/history/core/browser/download_types.h"
 
 namespace sql {
@@ -113,6 +114,16 @@ class DownloadDatabase {
 
   void RemoveDownloadURLs(uint32_t id);
 
+  // Creates a new download job. Returns true on success, or false otherwise.
+  bool CreateDownloadJob(const DownloadJobInfo& info);
+
+  // Updates the state of a download job. Returns true on success, or false
+  // if the job doesn't exists..
+  bool UpdateDownloadJob(const DownloadJobInfo& info);
+
+  // Delete all the download jobs associated with one DownloadRow.
+  void RemoveDownloadJobs(uint32_t id);
+
   bool owning_thread_set_;
   base::PlatformThreadId owning_thread_;