Adding MHTML support into Page Load Metrics

chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc

Index: chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc
diff --git a/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc b/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc
index 4b5b431d0629c7146668e8a856fa3e51ac45cfce..eba83de498a0fb1f1b506f1645e5c0f583a05fde 100644
--- a/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc
+++ b/chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.cc
@@ -4,8 +4,6 @@
 
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 
-#include <string>
-
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_util.h"
@@ -50,6 +48,17 @@ PreviewsPageLoadMetricsObserver::OnCommit(
              : STOP_OBSERVING;
 }
 
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+PreviewsPageLoadMetricsObserver::ShouldObserveMimeType(
+    const std::string& mime_type) const {
+  // Support observing HTML, XHTML, and MHTML. Offline previews are served as
+  // MHTML (multipart/related).
+  return mime_type == "text/html" || mime_type == "application/xhtml+xml" ||

[Bryan McQuade, 2017/02/21 18:50:15]

let's have this chain to the base class impl first, and if true, return true,
then also allow multipart/related:

if (PageLoadMetricsObserver::ShouldObserveMimeType(mime_type) ==
CONTINUE_OBSERVING)
  return CONTINUE_OBSERVING;
return mime_type == "multipart/related" ? CONTINUE_OBSERVING : STOP_OBSERVING;

or some variation of this.

+                 mime_type == "multipart/related"
+             ? CONTINUE_OBSERVING
+             : STOP_OBSERVING;
+}
+
 void PreviewsPageLoadMetricsObserver::OnDomContentLoadedEventStart(
     const page_load_metrics::PageLoadTiming& timing,
     const page_load_metrics::PageLoadExtraInfo& info) {