Refactor to move chrome_page_zoom functions to components/ui/zoom.

components/ui/zoom/page_zoom_constants.h

+// 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.
+
+#ifndef COMPONENTS_UI_ZOOM_PAGE_ZOOM_CONSTANTS_H_
+#define COMPONENTS_UI_ZOOM_PAGE_ZOOM_CONSTANTS_H_
+
+#include <vector>
+
+namespace ui_zoom {
+
+// Default zoom factors supported by ui_zoom.
+extern const double kPresetZoomFactors[];
+
+// Size of |kPresetZoomFactors|.
+extern const std::size_t kPresetZoomFactorsSize;
+
+}  // namespace ui_zoom
+
+#endif  // COMPONENTS_UI_ZOOM_PAGE_ZOOM_CONSTANTS_H_