Implement a basic Site Engagement Score service.

chrome/browser/engagement/site_engagement_helper.cc

Index: chrome/browser/engagement/site_engagement_helper.cc
diff --git a/chrome/browser/engagement/site_engagement_helper.cc b/chrome/browser/engagement/site_engagement_helper.cc
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+++ b/chrome/browser/engagement/site_engagement_helper.cc
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+// 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 "chrome/browser/engagement/site_engagement_helper.h"
+
+#include "chrome/browser/engagement/site_engagement_service.h"
+#include "chrome/browser/engagement/site_engagement_service_factory.h"
+#include "chrome/browser/prerender/prerender_contents.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/navigation_entry.h"
+#include "content/public/browser/web_contents.h"
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(SiteEngagementHelper);
+
+SiteEngagementHelper::~SiteEngagementHelper() {
+}
+
+SiteEngagementHelper::SiteEngagementHelper(content::WebContents* web_contents)
+    : content::WebContentsObserver(web_contents) {
+}
+
+void SiteEngagementHelper::DidStartNavigationToPendingEntry(
+    const GURL& url,
+    content::NavigationController::ReloadType reload_type) {
+  prerender::PrerenderContents* prerender_contents =
+      prerender::PrerenderContents::FromWebContents(web_contents());
+
+  // Ignore pre-render loads.
+  if (prerender_contents != NULL)
+    return;
+
+  // Ignore all schemes except HTTP and HTTPS.
+  if (!url.SchemeIsHTTPOrHTTPS())
+    return;
+
+  Profile* profile =
+      Profile::FromBrowserContext(web_contents()->GetBrowserContext());
+  SiteEngagementService* service =
+      SiteEngagementServiceFactory::GetForProfile(profile);
+  DCHECK(service);
+
+  service->HandleNavigation(url);
+}