add a download slices table into history download db

components/history/core/browser/history_database.cc

Index: components/history/core/browser/history_database.cc
diff --git a/components/history/core/browser/history_database.cc b/components/history/core/browser/history_database.cc
index 9810c5c1c94d84e394a7c7ba792679a656210752..e140b9562e4fd57bf7c30dce43fd88ce405ffe6b 100644
--- a/components/history/core/browser/history_database.cc
+++ b/components/history/core/browser/history_database.cc
@@ -36,7 +36,7 @@ namespace {
 // Current version number. We write databases at the "current" version number,
 // but any previous version that can read the "compatible" one can make do with
 // our database without *too* many bad effects.
-const int kCurrentVersionNumber = 32;
+const int kCurrentVersionNumber = 33;
 const int kCompatibleVersionNumber = 16;
 const char kEarlyExpirationThresholdKey[] = "early_expiration_threshold";
 const int kMaxHostsInMemory = 10000;
@@ -536,6 +536,11 @@ sql::InitStatus HistoryDatabase::EnsureCurrentVersion() {
     meta_table_.SetVersionNumber(cur_version);
   }
 
+  if (cur_version == 32) {
+    // New download jobs table is introduced, no migration needed.
+    cur_version++;
+    meta_table_.SetVersionNumber(cur_version);
+  }

[Scott Hess - ex-Googler, 2017/02/06 21:22:16]

maintain the whitespace line between clauses.

[qinmin, 2017/02/06 23:39:22]

Done.

   // When the version is too old, we just try to continue anyway, there should
   // not be a released product that makes a database too old for us to handle.
   LOG_IF(WARNING, cur_version < GetCurrentVersion()) <<