[page_load_metrics] Add support for chrome:// urls and add extensions observer

chrome/browser/page_load_metrics/browser_page_track_decider.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/page_load_metrics/browser_page_track_decider.h"
 
 #include <string>
 
 #include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/web_contents.h"
 #include "net/http/http_response_headers.h"
+#include "url/url_constants.h"
 
 namespace page_load_metrics {
 
 BrowserPageTrackDecider::BrowserPageTrackDecider(
     PageLoadMetricsEmbedderInterface* embedder_interface,
     content::WebContents* web_contents,
     content::NavigationHandle* navigation_handle)
     : embedder_interface_(embedder_interface),
       web_contents_(web_contents),
       navigation_handle_(navigation_handle) {}
 
 BrowserPageTrackDecider::~BrowserPageTrackDecider() {}
 
 bool BrowserPageTrackDecider::HasCommitted() {
   return navigation_handle_->HasCommitted();
 }
 
-bool BrowserPageTrackDecider::IsHttpOrHttpsUrl() {
-  return navigation_handle_->GetURL().SchemeIsHTTPOrHTTPS();
-}
-
 bool BrowserPageTrackDecider::IsNewTabPageUrl() {
   return embedder_interface_->IsNewTabPageUrl(navigation_handle_->GetURL());
 }
 
+bool BrowserPageTrackDecider::IsAboutBlankUrl() {
+  return navigation_handle_->GetURL() == GURL(url::kAboutBlankURL);
+}
+
 bool BrowserPageTrackDecider::IsChromeErrorPage() {
   DCHECK(HasCommitted());
   return navigation_handle_->IsErrorPage();
 }
 
 int BrowserPageTrackDecider::GetHttpStatusCode() {
   DCHECK(HasCommitted());
   const net::HttpResponseHeaders* response_headers =
       navigation_handle_->GetResponseHeaders();
   if (!response_headers)
     return -1;
   return response_headers->response_code();
 }
 
 bool BrowserPageTrackDecider::IsHtmlOrXhtmlPage() {
   DCHECK(HasCommitted());
   const std::string& mime_type = web_contents_->GetContentsMimeType();
   return mime_type == "text/html" || mime_type == "application/xhtml+xml";
 }
 
 }  // namespace page_load_metrics