Factor DRP PreviewsState logic out of content

components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc

 // Copyright 2014 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 "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
@@ skipping 25 matching lines @@
     "chrome-proxy-accept-transform";
 const char kChromeProxyContentTransformHeader[] =
     "chrome-proxy-content-transform";
 
 const char kActionValueDelimiter = '=';
 
 // Previews directives.
 const char kEmptyImageDirective[] = "empty-image";
 const char kLitePageDirective[] = "lite-page";
 const char kCompressedVideoDirective[] = "compressed-video";
+const char kChromeProxyPagePoliciesDirective[] = "page-policies";
 
 // The legacy Chrome-Proxy response header directive for LoFi images.
 const char kLegacyChromeProxyLoFiResponseDirective[] = "q=low";
 
 const char kChromeProxyExperimentForceLitePage[] = "force_lite_page";
 const char kChromeProxyExperimentForceEmptyImage[] =
     "force_page_policies_empty_image";
 
 const char kIfHeavyQualifier[] = "if-heavy";
 
@@ skipping 94 matching lines @@
 }
 
 const char* lite_page_directive() {
   return kLitePageDirective;
 }
 
 const char* compressed_video_directive() {
   return kCompressedVideoDirective;
 }
 
+const char* page_policies_directive() {
+  return kChromeProxyPagePoliciesDirective;
+}
+
 const char* chrome_proxy_experiment_force_lite_page() {
   return kChromeProxyExperimentForceLitePage;
 }
 
 const char* chrome_proxy_experiment_force_empty_image() {
   return kChromeProxyExperimentForceEmptyImage;
 }
 
 const char* if_heavy_qualifier() {
   return kIfHeavyQualifier;
@@ skipping 265 matching lines @@
   std::string value;
   size_t iter = 0;
   while (headers->EnumerateHeader(&iter, kChromeProxyHeader, &value)) {
     if (StartsWithActionPrefix(value, kChromeProxyActionFingerprintChromeProxy))
       continue;
     values->push_back(std::move(value));
   }
 }
 
 }  // namespace data_reduction_proxy