[PM] Increase the site characteristic database version.

Favicon and title that happened in response to a user action, just
after a tab was backgrounded, were incorrectly tracked as signals
that the page is trying to communicate with the user in background.
Now that this issue is fixed, we are increasing the DB version to
automatically delete all the incorrect data.

No-Try: true
Bug: 1014976
Change-Id: If6bb9816d3a5f57d5daa12a53812c2f2d3a3b84f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865601
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707001}

chrome/browser/resource_coordinator/leveldb_site_characteristics_database.cc

@@ -102,10 +102,16 @@ struct DatabaseSizeResult {
 //       after a tab being loaded.
 //     - Ignore the audio events happening during the first fews seconds after a
 //       tab being backgrounded.
+// - 2:
+//     - Ignore events that happen shortly after a tab is backgrounded. This is
+//       because such events are likely a response to a recent user action
+//       rather than an attempt from the tab to communicate in background.
+//       See https://crbug.com/1865601.
 //
 // Transform logic:
-//     - From {no version} to v1: The database is erased entirely.
-const size_t LevelDBSiteCharacteristicsDatabase::kDbVersion = 1U;
+//     - From any version to v1: The database is erased entirely.
+//     - From any version to v2: The database is erased entirely.
+const size_t LevelDBSiteCharacteristicsDatabase::kDbVersion = 2U;
 
 const char LevelDBSiteCharacteristicsDatabase::kDbMetadataKey[] =
     "database_metadata";