Plumb experiment flags through page_load_metrics and add a new observer

components/page_load_metrics/common/page_load_timing.h

 // 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.
 
 #ifndef COMPONENTS_PAGE_LOAD_METRICS_COMMON_PAGE_LOAD_TIMING_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_COMMON_PAGE_LOAD_TIMING_H_
 
 #include "base/time/time.h"
+#include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
 
 namespace page_load_metrics {
 
 // PageLoadTiming contains timing metrics associated with a page load. Many of
 // the metrics here are based on the Navigation Timing spec:
 // http://www.w3.org/TR/navigation-timing/.
 struct PageLoadTiming {
  public:
   PageLoadTiming();
   PageLoadTiming(const PageLoadTiming& other);
@@ skipping 40 matching lines @@
 
   // Sum of times when the parser is blocked waiting on the load of a script.
   // This duration takes place between parser_start and parser_stop, and thus
   // must be less than or equal to parser_stop - parser_start.
   base::TimeDelta parse_blocked_on_script_load_duration;
 
   // If you add additional members, also be sure to update operator==,
   // page_load_metrics_messages.h, and IsEmpty().
 };
 
+struct PageLoadMetadata {
+  PageLoadMetadata();
+  bool operator==(const PageLoadMetadata& other) const;
+  // These are packed blink::WebLoadingBehaviorFlag enums.
+  int behavior_flags = blink::WebLoadingBehaviorNone;
+};
+
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_COMMON_PAGE_LOAD_TIMING_H_