Change insertId to be int64_t to match the sqlite API.

This avoids a possible truncation warning.

BUG=879657

Change-Id: I533c053523c8ade81bb54b55071d4d509e834cbb
Reviewed-on: https://chromium-review.googlesource.com/c/1348970Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610636}

third_party/blink/renderer/modules/webdatabase/sql_result_set.idl

@@ -32,6 +32,6 @@
 ] interface SQLResultSet {
     readonly attribute SQLResultSetRowList rows;
 
-    [RaisesException=Getter] readonly attribute long insertId;
+    [RaisesException=Getter] readonly attribute long long insertId;
     readonly attribute long rowsAffected;
 };