Remove quota if set to zero

When site data is removed, persistent quota gets resetted to zero.
Instead of keeping the origin in the database, we should just delete it
to remove traces of browsing_data.

Bug: 849677
Change-Id: Ice2282274012fe8d2cb65bbac0b328523e8ce666
Reviewed-on: https://chromium-review.googlesource.com/1087057Reviewed-by: Taiju Tsuiki <tzik@chromium.org>
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564821}

storage/browser/quota/quota_database.cc

@@ -198,6 +198,8 @@ bool QuotaDatabase::SetHostQuota(const std::string& host,
   DCHECK_GE(quota, 0);
   if (!LazyOpen(true))
     return false;
+  if (quota == 0)
+    return DeleteHostQuota(host, type);
   if (!InsertOrReplaceHostQuota(host, type, quota))
     return false;
   ScheduleCommit();

storage/browser/quota/quota_database_unittest.cc

@@ -112,6 +112,10 @@ class QuotaDatabaseTest : public testing::Test {
     // Delete temporary storage quota.
     EXPECT_TRUE(db.DeleteHostQuota(kHost, kTemporary));
     EXPECT_FALSE(db.GetHostQuota(kHost, kTemporary, &quota));
+
+    // Delete persistent quota by setting it to zero.
+    EXPECT_TRUE(db.SetHostQuota(kHost, kPersistent, 0));
+    EXPECT_FALSE(db.GetHostQuota(kHost, kPersistent, &quota));
   }
 
   void GlobalQuota(const base::FilePath& kDbFile) {