Add UMA to determine how often we offline a page with previews.

chrome/browser/loader/chrome_navigation_data.cc

 // 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.
 
 #include "chrome/browser/loader/chrome_navigation_data.h"
 
 #include "base/memory/ptr_util.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_data.h"

[RyanSturm, 2017/06/02 20:50:33]

Don't need data_reduction_proxy_data.h included in the header and here.

[Pete Williamson, 2017/06/02 21:40:32]

Done.

 #include "net/url_request/url_request.h"
 
 const void* const kChromeNavigationDataUserDataKey =
     &kChromeNavigationDataUserDataKey;
 
-ChromeNavigationData::ChromeNavigationData() {}
+ChromeNavigationData::ChromeNavigationData()
+    : previews_state_(content::PreviewsTypes::PREVIEWS_UNSPECIFIED) {}
 
 ChromeNavigationData::~ChromeNavigationData() {}
 
 ChromeNavigationData* ChromeNavigationData::GetDataAndCreateIfNecessary(
     net::URLRequest* request) {
   if (!request)
     return nullptr;
   ChromeNavigationData* data = static_cast<ChromeNavigationData*>(
       request->GetUserData(kChromeNavigationDataUserDataKey));
   if (data)
     return data;
   data = new ChromeNavigationData();
   request->SetUserData(kChromeNavigationDataUserDataKey,
                        base::WrapUnique(data));
   return data;
 }
 
 std::unique_ptr<content::NavigationData> ChromeNavigationData::Clone() const {
   std::unique_ptr<ChromeNavigationData> copy(new ChromeNavigationData());
   if (data_reduction_proxy_data_)

[RyanSturm, 2017/06/02 20:50:33]

You need to also copy the previews state over.

[Pete Williamson, 2017/06/02 21:40:32]

Done.

     copy->SetDataReductionProxyData(data_reduction_proxy_data_->DeepCopy());
   return std::move(copy);
 }