Update OnCommit to return ObservePolicy.

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
index 0a1bf48d2475c23ef94aaf2c9fa5c120d7301306..f1f3e3fbe2eaef57f7f89ba03fc77425a04cacf7 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
@@ -442,8 +442,14 @@ void PageLoadTracker::Commit(content::NavigationHandle* navigation_handle) {
   // 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);
 }