[Quota] Add UsageTracker::GetGlobalLimitedUsage

webkit/quota/quota_temporary_storage_evictor.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/quota/quota_temporary_storage_evictor.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
@@ skipping 148 matching lines @@
   quota_eviction_handler_->GetUsageAndQuotaForEviction(
       base::Bind(&QuotaTemporaryStorageEvictor::OnGotUsageAndQuotaForEviction,
                  weak_factory_.GetWeakPtr()));
 }
 
 void QuotaTemporaryStorageEvictor::OnGotUsageAndQuotaForEviction(
     QuotaStatusCode status,
     const UsageAndQuota& qau) {
   DCHECK(CalledOnValidThread());
 
-  // unlimited_usage is a subset of usage
-  DCHECK_GE(qau.global_usage, qau.global_unlimited_usage);
-
-  int64 usage = qau.global_usage - qau.global_unlimited_usage;
+  int64 usage = qau.global_limited_usage;
+  DCHECK_GE(usage, 0);
 
   if (status != kQuotaStatusOk)
     ++statistics_.num_errors_on_getting_usage_and_quota;
 
   int64 usage_overage = std::max(
       static_cast<int64>(0),
       usage - static_cast<int64>(qau.quota * kUsageRatioToStartEviction));
 
   // min_available_disk_space_to_start_eviction_ might be < 0 if no value
   // is explicitly configured yet.
@@ skipping 71 matching lines @@
     ++statistics_.num_errors_on_evicting_origin;
     if (repeated_eviction_) {
       // Sleep for a while and retry again until we see too many errors.
       StartEvictionTimerWithDelay(interval_ms_);
     }
     OnEvictionRoundFinished();
   }
 }
 
 }  // namespace quota