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

chrome/renderer/page_load_metrics/renderer_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/renderer/page_load_metrics/renderer_page_track_decider.h"
 
 #include <string>
 
 #include "chrome/renderer/searchbox/search_bouncer.h"
 #include "third_party/WebKit/public/platform/WebURLResponse.h"
 #include "third_party/WebKit/public/web/WebDataSource.h"
 #include "third_party/WebKit/public/web/WebDocument.h"
 #include "url/gurl.h"
+#include "url/url_constants.h"
 
 namespace page_load_metrics {
 
 RendererPageTrackDecider::RendererPageTrackDecider(
     const blink::WebDocument* document,
     const blink::WebDataSource* data_source)
     : document_(document), data_source_(data_source) {}
 
 RendererPageTrackDecider::~RendererPageTrackDecider() {}
 
 bool RendererPageTrackDecider::HasCommitted() {
   // RendererPageTrackDecider is only instantiated for committed pages.
   return true;
 }
 
-bool RendererPageTrackDecider::IsHttpOrHttpsUrl() {
-  return static_cast<GURL>(document_->url()).SchemeIsHTTPOrHTTPS();
-}
-
 bool RendererPageTrackDecider::IsNewTabPageUrl() {
   return SearchBouncer::GetInstance()->IsNewTabPage(document_->url());
 }
 
+bool RendererPageTrackDecider::IsAboutBlankUrl() {
+  return document_->url().string() == url::kAboutBlankURL;
+}
+
 bool RendererPageTrackDecider::IsChromeErrorPage() {
   return data_source_->hasUnreachableURL();
 }
 
 int RendererPageTrackDecider::GetHttpStatusCode() {
   return data_source_->response().httpStatusCode();
 }
 
 bool RendererPageTrackDecider::IsHtmlOrXhtmlPage() {
   // Ignore non-HTML documents (e.g. SVG). Note that images are treated by
   // Blink as HTML documents, so to exclude images, we must perform
   // additional mime type checking below.
   if (!document_->isHTMLDocument() && !document_->isXHTMLDocument())
     return false;
 
   // Ignore non-HTML mime types (e.g. images).
   blink::WebString mime_type = data_source_->response().mimeType();
   return mime_type == "text/html" || mime_type == "application/xhtml+xml";
 }
 
 }  // namespace page_load_metrics