Refactoring recently closed tab filtering

chrome/browser/sessions/session_utils.cc

Index: chrome/browser/sessions/session_utils.cc
diff --git a/chrome/browser/sessions/session_utils.cc b/chrome/browser/sessions/session_utils.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8ae293c41e989b6012732d35242ae80f5429f24b
--- /dev/null
+++ b/chrome/browser/sessions/session_utils.cc
@@ -0,0 +1,61 @@
+// 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 "chrome/browser/sessions/session_utils.h"
+
+#include <set>
+
+#include "chrome/browser/sessions/tab_restore_service.h"
+
+namespace {
+
+// This class is used to compare two entries and considers that they are
+// identical if they share the same URL. See FilteredEntries() below for how
+// this is used.
+class EntryComparator {
+ public:
+  bool operator() (const TabRestoreService::Entry* lhs,
+                   const TabRestoreService::Entry* rhs) {
+    // Two entries are deemed identical when their visible title and URL are
+    // the same.
+    if (lhs->type == TabRestoreService::WINDOW ||
+        rhs->type == TabRestoreService::WINDOW)
+      return false;
+
+    DCHECK(lhs->type == TabRestoreService::TAB);
+    DCHECK(rhs->type == TabRestoreService::TAB);
+
+    const TabRestoreService::Tab* rh_tab =
+    static_cast<const TabRestoreService::Tab*>(rhs);
+    const TabRestoreService::Tab* lh_tab =
+    static_cast<const TabRestoreService::Tab*>(lhs);
+
+    const TabNavigation& rh_entry =
+    rh_tab->navigations[rh_tab->current_navigation_index];
+    const TabNavigation& lh_entry =
+    lh_tab->navigations[lh_tab->current_navigation_index];
+
+    if (rh_entry.title() == lh_entry.title())
+      return rh_entry.virtual_url().spec() < lh_entry.virtual_url().spec();
+
+    return rh_entry.title() < lh_entry.title();
+  }
+};
+}  // namespace
+
+void SessionUtils::FilteredEntries(const TabRestoreService::Entries& entries,
+    TabRestoreService::Entries* filtered_entries) {
+  // A set to remember the entries we already seen.
+  std::set<TabRestoreService::Entry*, EntryComparator> uniquing;
+
+  for (TabRestoreService::Entries::const_iterator iter = entries.begin();
+       iter != entries.end(); ++iter) {
+    TabRestoreService::Entry* entry = *iter;
+
+    if (uniquing.insert(entry).second)
+      // This entry was not seen before, add it to the list.
+      filtered_entries->push_back(entry);
+  }
+}
+