Change Lo-Fi bool to bitmask to support multiple Previews types

content/public/common/previews_state.h

+// Copyright 2016 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 CONTENT_PUBLIC_COMMON_PREVIEWS_TYPE_H_
+#define CONTENT_PUBLIC_COMMON_PREVIEWS_TYPE_H_
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+// The Previews state which determines whether to request a Preview version of
+// the resource.
+enum PreviewsState {
+  PREVIEWS_UNSPECIFIED = 1 << 0, // Let the browser process decide whether or

[RyanSturm, 2016/12/03 00:28:11]

I don't think UNSPECIFIED is necessary, but I might not have thought it through.
Is it possible to have UNSPECIFIED set and have another bit set, or can 0
represent an unspecified state? It might be a good idea to have
PREVIEWS_UNSPECIFIED = 0 and do an explicit previews_state ==
PREVIEWS_UNSPECIFIED as opposed to a bitwise and for that case.

[megjablon, 2016/12/06 00:59:18]

Done.

+                                 // not to request Preview types.
+  SERVER_LOFI_ON = 1 << 1,       // Request a Lo-Fi version of the resource
+                                 // from the server.
+  CLIENT_LOFI_ON = 1 << 2,       // Request a Lo-Fi version of the resource
+                                 // from the client.
+  PREVIEWS_OFF = 1 << 3          // Request a normal (non-Preview) version of
+                                 // the resource.
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_COMMON_PREVIEWS_TYPE_H_