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

chrome/browser/page_load_metrics/browser_page_track_decider.cc

Index: chrome/browser/page_load_metrics/browser_page_track_decider.cc
diff --git a/chrome/browser/page_load_metrics/browser_page_track_decider.cc b/chrome/browser/page_load_metrics/browser_page_track_decider.cc
index 8b09eae2a2535ccdd9b3b850fd135faa2e45b4ff..5e7383d78a260fad36bc21df7e1b527e4e5212fb 100644
--- a/chrome/browser/page_load_metrics/browser_page_track_decider.cc
+++ b/chrome/browser/page_load_metrics/browser_page_track_decider.cc
@@ -10,6 +10,7 @@
 #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 {
 
@@ -27,14 +28,14 @@ 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();