Add PLMObserver::FlushMetricsOnAppEnterBackground.

chrome/browser/page_load_metrics/page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
index 6ac706be85a0eefabdb90c4347c877fcb0ed8030..7608bc2df6c226b0fbef5ebdfe2cb9cb6e32a5f7 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
@@ -44,4 +44,11 @@ FailedProvisionalLoadInfo::FailedProvisionalLoadInfo(base::TimeDelta interval,
 
 FailedProvisionalLoadInfo::~FailedProvisionalLoadInfo() {}
 
+PageLoadMetricsObserver::ObservePolicy
+PageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
+    const PageLoadTiming& timing,
+    const PageLoadExtraInfo& extra_info) {
+  return CONTINUE_OBSERVING;
+}
+
 }  // namespace page_load_metrics