Introduce the NotificationIdGenerator in //content.

content/browser/notifications/notification_id_generator.cc

Index: content/browser/notifications/notification_id_generator.cc
diff --git a/content/browser/notifications/notification_id_generator.cc b/content/browser/notifications/notification_id_generator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9dc9725c6880e0a2ebd4895856be1b184407267c
--- /dev/null
+++ b/content/browser/notifications/notification_id_generator.cc
@@ -0,0 +1,70 @@
+// Copyright 2015 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 "content/browser/notifications/notification_id_generator.h"
+
+#include <sstream>
+
+#include "base/files/file_path.h"
+#include "base/hash.h"
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "content/public/browser/browser_context.h"
+#include "url/gurl.h"
+
+namespace content {
+
+NotificationIdGenerator::NotificationIdGenerator(
+    BrowserContext* browser_context,
+    int render_process_id)
+    : browser_context_(browser_context),
+      render_process_id_(render_process_id) {}
+
+NotificationIdGenerator::~NotificationIdGenerator() {}
+
+std::string NotificationIdGenerator::GenerateForPersistentNotification(
+    const GURL& origin,
+    const std::string& tag,
+    int64_t persistent_notification_id) const {
+  std::stringstream stream;
+
+  stream << base::Hash(browser_context_->GetPath().value());

[johnme, 2015/05/08 15:35:25]

base::Hash is just 32-bits, and not a secure hash. So there's a nontrivial
chance of these colliding, for at least some users.

[Peter Beverloo, 2015/05/20 18:43:33]

What would you propose to do instead, without overcomplicating this?

+  stream << browser_context_->IsOffTheRecord();
+  stream << origin.GetOrigin();

[johnme, 2015/05/08 15:35:25]

This is ambiguous. The following two cases will give the same output:

origin = https://example.com:805
tag = 17

origin = https://example.com:8051
tag = 7

In both cases the generated string will end with 5117

[Peter Beverloo, 2015/05/20 18:43:33]

They wouldn't, because origins end with slashes. :-)

Added a test anyway in case we ever decide to change this.

+
+  // Persistent notification ids are unique for the lifetime of the notification
+  // database, orthogonal to the renderer that created the notification.
+
+  stream << !!tag.size();
+  if (tag.size())
+    stream << tag;
+  else
+    stream << base::Int64ToString(persistent_notification_id);
+
+  return stream.str();
+}
+
+std::string NotificationIdGenerator::GenerateForNonPersistentNotification(
+    const GURL& origin,
+    const std::string& tag,
+    int non_persistent_notification_id) const {
+  std::stringstream stream;
+
+  stream << base::Hash(browser_context_->GetPath().value());
+  stream << browser_context_->IsOffTheRecord();
+  stream << origin.GetOrigin();
+
+  // Non-persistent notification ids are unique per renderer process.
+  stream << render_process_id_;

[johnme, 2015/05/08 15:35:25]

This is ambiguous. The following two cases will give the same output:

render_process_id_ = 5
tag = 17

render_process_id_ = 51
tag = 7

In both cases the generated string will end with 5117

[Peter Beverloo, 2015/05/20 18:43:33]

Fixed, and added a test.

+
+  stream << !!tag.size();
+  if (tag.size())
+    stream << tag;
+  else
+    stream << base::IntToString(non_persistent_notification_id);
+
+  return stream.str();
+}
+
+}  // namespace content