Adding MHTML support into Page Load Metrics

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 a27936877739c38686a1e84fe71353e113be172d..673e7247ac28e81cd17b5bd0880c9a56ddad833b 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_observer.cc
@@ -85,4 +85,12 @@ PageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
   return CONTINUE_OBSERVING;
 }
 
+PageLoadMetricsObserver::ObservePolicy
+PageLoadMetricsObserver::ShouldObserveMimeType(
+    const std::string& mime_type) const {
+  return mime_type == "text/html" || mime_type == "application/xhtml+xml"
+             ? CONTINUE_OBSERVING
+             : STOP_OBSERVING;
+}
+
 }  // namespace page_load_metrics