Proposal: Provide the ability to monitor the usage of origins

webkit/browser/quota/storage_observer.h

+// Copyright 2014 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.
+
+#ifndef WEBKIT_BROWSER_QUOTA_STORAGE_OBSERVER_H_
+#define WEBKIT_BROWSER_QUOTA_STORAGE_OBSERVER_H_
+
+#include "base/basic_types.h"
+#include "url/gurl.h"
+#include "webkit/browser/quota/quota_client.h"
+#include "webkit/browser/quota/quota_types.h"
+
+namespace quota {
+
+// This interface is implemented by subsystems that wish to monitor storage
+// events, such as changes in quota or usage.
+class WEBKIT_STORAGE_BROWSER_EXPORT StorageObserver {
+ public:
+  struct WEBKIT_STORAGE_BROWSER_EXPORT Filter {
+    // The storage type to monitor. This must not be kStorageTypeUnknown.
+    StorageType storage_type;
+
+    // The quota client to monitor. This can be kAllClientsMask to monitor the
+    // aggregated usage for the given storage type and origin. In this case, the
+    // threshold will apply to the accumulated total usage.

[nhiroki, 2014/03/17 06:41:51]

"In this case, ..." seems to be deprecated by PatchSet 2.

+    QuotaClient::ID client_id;
+
+    // The origin to monitor usage for. Must be specified.
+    GURL origin;
+
+    Filter();
+  };
+
+  struct WEBKIT_STORAGE_BROWSER_EXPORT MonitorParams {
+    // Storage types and origin to monitor.
+    Filter filter;
+
+    // The rate (in seconds) at which storage events will be fired.
+    // Events will be fired at approximately this rate, or when a storage status
+    // change has been detected, whichever is the least frequent.
+    int rate;
+
+    MonitorParams();
+  };
+
+  struct WEBKIT_STORAGE_BROWSER_EXPORT Event {
+    // The storage types and origin monitored.
+    Filter filter;
+
+    // The current usage corresponding to the filter.
+    int64 usage;
+
+    // The quota corresponding to the filter.
+    int64 quota;

[nhiroki, 2014/03/17 06:41:51]

What does |quota| contains when the aggregated usage is notified (that is,
|client_id| is kAllClientsMask)?

[nhiroki, 2014/03/17 07:23:22]

Oops... sorry I misunderstood. I thought "aggregated usage" means a sum of all
origins. Please ignore this comment.

+
+    Event();
+  };
+
+  // Will be called when a storage event occurs.
+  virtual void OnStorageEvent(const Event& event) = 0;
+
+ protected:
+  virtual ~StorageObserver() {}
+};
+
+}  // namespace quota
+
+#endif  // WEBKIT_BROWSER_QUOTA_STORAGE_OBSERVER_H_