Introduce the NotificationIdGenerator in //content.

content/browser/notifications/notification_id_generator.cc

+// 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/logging.h"
+#include "base/sha1.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/utf_string_conversions.h"
+#include "content/public/browser/browser_context.h"
+#include "url/gurl.h"
+
+namespace content {
+namespace {
+
+const char kSeparator = '#';
+
+// Computes a hash based on the path in which the |browser_context| is stored.
+// This hash might be used outside of Chrome (e.g. the platform's notification
+// manager), thus SHA-1 is used to maximise preimage resistance.

[johnme, 2015/05/29 09:34:57]

Nit: "preimage resistance" is somewhat obscure, and I also don't think it's
technically correct (since you don't care if an attacker can craft an input
which hashes to a desired value, you just care whether the inputs generated by
Chrome ever collide). It's also not particularly relevant that it's used outside
of Chrome (any attacker outside of Chrome will have access to the filesystem,
and can easily enumerate Chrome profile paths). I'd replace the entire last
sentence with "Since we only store the hash, SHA-1 is used to make the
probability of collisions negligible.".

[Peter Beverloo, 2015/05/29 12:34:08]

Done.

+std::string ComputeBrowserContextHash(BrowserContext* browser_context) {
+  const base::FilePath path = browser_context->GetPath();
+
+#if defined(OS_WIN)
+  return base::SHA1HashString(base::WideToUTF8(path.value()));
+#else
+  return base::SHA1HashString(path.value());
+#endif
+}
+
+}  // namespace
+
+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 {
+  DCHECK(origin.is_valid());
+  DCHECK_EQ(origin, origin.GetOrigin());
+
+  std::stringstream stream;
+
+  stream << ComputeBrowserContextHash(browser_context_);
+  stream << browser_context_->IsOffTheRecord();
+  stream << origin;
+
+  // 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);

[johnme, 2015/05/29 09:34:57]

Nit: the base::Int64ToString is presumably unnecessary (see below). So either
remove it, or add IntToString for render_process_id_.

[Peter Beverloo, 2015/05/29 12:34:08]

Done.

+
+  return stream.str();
+}
+
+std::string NotificationIdGenerator::GenerateForNonPersistentNotification(
+    const GURL& origin,
+    const std::string& tag,
+    int non_persistent_notification_id) const {
+  DCHECK(origin.is_valid());
+  DCHECK_EQ(origin, origin.GetOrigin());
+
+  std::stringstream stream;
+
+  stream << ComputeBrowserContextHash(browser_context_);
+  stream << browser_context_->IsOffTheRecord();
+  stream << origin;
+
+  // Non-persistent notification ids are unique per renderer process when no
+  // tag is being used. Tags still identify uniqueness for the given origin.
+
+  stream << !!tag.size();
+  if (!tag.size()) {
+    stream << render_process_id_;
+    stream << kSeparator;
+
+    stream << base::IntToString(non_persistent_notification_id);

[johnme, 2015/05/29 09:34:57]

Nit: the base::IntToString seems unnecessary, since << can convert ints to
string (as you do for render_process_id_ above). So either remove it, or add it
for render_process_id_.

[Peter Beverloo, 2015/05/29 12:34:08]

Done.

+  } else {
+    stream << tag;
+  }
+
+  return stream.str();
+}
+
+}  // namespace content