Adds Server Previews protocol UMA plus UMA for not accepting previews

components/data_reduction_proxy/content/browser/content_lofi_decider_unittest.cc

 // 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.
 
 #include "components/data_reduction_proxy/content/browser/content_lofi_decider.h"
 
 #include <stddef.h>
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 753 matching lines @@
 
 TEST_F(ContentLoFiDeciderTest, VideoDirectiveDoesNotOverride) {
   base::FieldTrialList field_trial_list(nullptr);
   base::FieldTrialList::CreateFieldTrial(params::GetLoFiFieldTrialName(),
                                          "Enabled");
   // Verify the directive gets added even when LoFi is triggered.
   test_context_->config()->SetNetworkProhibitivelySlow(true);
   std::unique_ptr<net::URLRequest> request =
       CreateRequestByType(content::RESOURCE_TYPE_MEDIA, false, true);
   net::HttpRequestHeaders headers;
-  headers.SetHeader(chrome_proxy_accept_transform_header(), "foo");
+  headers.SetHeader(chrome_proxy_accept_transform_header(), "empty-image");
   NotifyBeforeSendHeaders(&headers, request.get(), true);
   std::string header_value;
   headers.GetHeader(chrome_proxy_accept_transform_header(), &header_value);
-  EXPECT_EQ("foo", header_value);
+  EXPECT_EQ("empty-image", header_value);
 }
 
 TEST_F(ContentLoFiDeciderTest, IsSlowPagePreviewRequested) {
   std::unique_ptr<data_reduction_proxy::ContentLoFiDecider> lofi_decider(
       new data_reduction_proxy::ContentLoFiDecider());
   net::HttpRequestHeaders headers;
   EXPECT_FALSE(lofi_decider->IsSlowPagePreviewRequested(headers));
   headers.SetHeader(chrome_proxy_accept_transform_header(), "lite-page");
   EXPECT_TRUE(lofi_decider->IsSlowPagePreviewRequested(headers));
   headers.SetHeader(chrome_proxy_accept_transform_header(), "lite-page;foo");
@@ skipping 93 matching lines @@
                            content::CLIENT_LOFI_AUTO_RELOAD)));
 
   // IsClientLoFiAutoReloadRequest() should return false for any request without
   // the CLIENT_LOFI_AUTO_RELOAD bit set.
   EXPECT_FALSE(ContentLoFiDecider().IsClientLoFiAutoReloadRequest(
       *CreateRequestByType(content::RESOURCE_TYPE_IMAGE, false,
                            content::PREVIEWS_NO_TRANSFORM)));
 }
 
 }  // namespace data_reduction_proxy