Update OnCommit to return ObservePolicy.

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

 // 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/page_load_metrics/metrics_web_contents_observer.h"
 
 #include <algorithm>
 #include <ostream>
 #include <string>
 #include <utility>
@@ skipping 424 matching lines @@
 
 void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
   // TODO(bmcquade): To improve accuracy, consider adding commit time to
   // NavigationHandle. Taking a timestamp here should be close enough for now.
   commit_time_ = base::TimeTicks::Now();
   ClampBrowserTimestampIfInterProcessTimeTickSkew(&commit_time_);
   url_ = navigation_handle->GetURL();
   // Some transitions (like CLIENT_REDIRECT) are only known at commit time.
   page_transition_ = navigation_handle->GetPageTransition();
   user_gesture_ = navigation_handle->HasUserGesture();
-  for (const auto& observer : observers_) {
-    observer->OnCommit(navigation_handle);
+
+  for (auto it = observers_.begin(); it != observers_.end();) {

[Charlie Harrison, 2016/09/27 16:32:48]

Refactor this to a common method?

[Bryan McQuade, 2016/09/27 18:00:14]

Sure, I factored it into a macro, per our conversation.

+    if ((*it)->OnCommit(navigation_handle) ==
+        PageLoadMetricsObserver::STOP_OBSERVING) {
+      it = observers_.erase(it);
+    } else {
+      ++it;
+    }
   }
   LogAbortChainHistograms(navigation_handle);
 }
 
 void PageLoadTracker::FailedProvisionalLoad(
     content::NavigationHandle* navigation_handle) {
   DCHECK(!failed_provisional_load_info_);
   failed_provisional_load_info_.reset(new FailedProvisionalLoadInfo(
       base::TimeTicks::Now() - navigation_handle->NavigationStart(),
       navigation_handle->GetNetErrorCode()));
@@ skipping 631 matching lines @@
     content::NavigationHandle* navigation_handle) const {
   DCHECK(navigation_handle->IsInMainFrame());
   DCHECK(!navigation_handle->HasCommitted() ||
          !navigation_handle->IsSamePage());
 
   return BrowserPageTrackDecider(embedder_interface_.get(), web_contents(),
                                  navigation_handle).ShouldTrack();
 }
 
 }  // namespace page_load_metrics