Adds Lo-Fi fallback support for new Data Reduction Proxy protocol.

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"
 #include "third_party/WebKit/public/platform/WebURLRequest.h"
 
 #define STATIC_ASSERT_PREVIEWS_ENUM(a, b)                   \
   static_assert(static_cast<int>(a) == static_cast<int>(b), \
                 "mismatching enums: " #a)
 
 namespace content {
 
-// Chrome Proxy Previews header and directives.
-const char kChromeProxyContentTransformHeader[] =
-    "chrome-proxy-content-transform";
-const char kChromeProxyEmptyImageDirective[] = "empty-image";
-const char kChromeProxyLitePageDirective[] = "lite-page";
-
 typedef int PreviewsState;
 
 // The Previews types which determines whether to request a Preview version of
 // the resource. Previews are optimizations that change the format and
 // content of web pages to improve data savings and / or performance. This enum
 // determines which Previews types to request.
 enum PreviewsTypes {
   PREVIEWS_UNSPECIFIED = 0,  // Let the browser process decide whether or
                              // not to request Preview types.
   SERVER_LOFI_ON = 1 << 0,   // Request a Lo-Fi version of the resource
@@ skipping 27 matching lines @@
                             blink::WebURLRequest::kServerLitePageOn);
 STATIC_ASSERT_PREVIEWS_ENUM(PREVIEWS_NO_TRANSFORM,
                             blink::WebURLRequest::kPreviewsNoTransform);
 STATIC_ASSERT_PREVIEWS_ENUM(PREVIEWS_OFF, blink::WebURLRequest::kPreviewsOff);
 STATIC_ASSERT_PREVIEWS_ENUM(PREVIEWS_STATE_LAST,
                             blink::WebURLRequest::kPreviewsStateLast);
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_COMMON_PREVIEWS_TYPE_H_