1 files changed, 43 insertions, 0 deletions
diff --git a/chromium/third_party/blink/renderer/core/page/named_pages_mapper.cc b/chromium/third_party/blink/renderer/core/page/named_pages_mapper.cc
new file mode 100644
index 00000000000..7a000869f81
--- /dev/null
+++ b/chromium/third_party/blink/renderer/core/page/named_pages_mapper.cc
@@ -0,0 +1,43 @@
+// Copyright 2020 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 "third_party/blink/renderer/core/page/named_pages_mapper.h"
+
+namespace blink {
+
+void NamedPagesMapper::AddNamedPage(const AtomicString& page_name,
+                                    int page_index) {
+  DCHECK_GE(entries_.size(), 1u);
+
+  // The last entry should have no last page set.
+  DCHECK_EQ(entries_.back().last_page_index, -1);
+
+  if (page_index > 0) {
+    auto prev_it = entries_.rbegin();
+    for (auto it = prev_it + 1; it != entries_.rend(); prev_it = it++) {
+      if (it->last_page_index < page_index)
+        break;
+    }
+
+    entries_.Shrink(entries_.rend() - prev_it);
+
+    // Terminate the previous entry (now that we know its last page index)
+    // before adding the new entry.
+    entries_.back().last_page_index = page_index - 1;
+  } else {
+    DCHECK_EQ(page_index, 0);
+    entries_.Shrink(0);
+  }
+  entries_.emplace_back(page_name);
+}
+
+const AtomicString& NamedPagesMapper::NamedPageAtIndex(int page_index) const {
+  for (const Entry& entry : entries_) {
+    if (page_index <= entry.last_page_index)
+      return entry.page_name;
+  }
+  return entries_.back().page_name;
+}
+
+}  // namespace blink