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

chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc

 // Copyright (c) 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/page_load_metrics/metrics_web_contents_observer.h"
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 301 matching lines @@
       content::WebContentsTester::For(web_contents());
 
   GURL about_blank_url = GURL("about:blank");
   web_contents_tester->NavigateAndCommit(about_blank_url);
   SimulateTimingUpdate(timing);
   ASSERT_EQ(0, CountUpdatedTimingReported());
   web_contents_tester->NavigateAndCommit(GURL(kDefaultTestUrl));
   ASSERT_EQ(0, CountUpdatedTimingReported());
   ASSERT_EQ(0, CountCompleteTimingReported());
 
-  CheckErrorEvent(ERR_IPC_FROM_BAD_URL_SCHEME, 1);
   CheckErrorEvent(ERR_IPC_WITH_NO_RELEVANT_LOAD, 1);
   CheckTotalErrorEvents();
 }
 
 TEST_F(MetricsWebContentsObserverTest, NotInMainError) {
   PageLoadTiming timing;
   timing.navigation_start = base::Time::FromDoubleT(1);
 
   content::WebContentsTester* web_contents_tester =
       content::WebContentsTester::For(web_contents());
@@ skipping 169 matching lines @@
 
   histogram_tester_.ExpectTotalCount(
       internal::kPageLoadCompletedAfterAppBackground, 2);
   histogram_tester_.ExpectBucketCount(
       internal::kPageLoadCompletedAfterAppBackground, false, 1);
   histogram_tester_.ExpectBucketCount(
       internal::kPageLoadCompletedAfterAppBackground, true, 1);
 }
 
 }  // namespace page_load_metrics