Report page load timing information for child frames.

chrome/browser/page_load_metrics/page_load_metrics_observer.h

Index: chrome/browser/page_load_metrics/page_load_metrics_observer.h
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_observer.h b/chrome/browser/page_load_metrics/page_load_metrics_observer.h
index c84787a443019d30ad4dcad76c606d1878f092f1..c828d9b5127d1cfa3143d0374f5a74d71477714d 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_observer.h
+++ b/chrome/browser/page_load_metrics/page_load_metrics_observer.h
@@ -270,6 +270,8 @@ class PageLoadMetricsObserver {
     STOP_OBSERVING,
   };
 
+  typedef int FrameTreeNodeId;
+
   virtual ~PageLoadMetricsObserver() {}
 
   // The page load started, with the given navigation handle.
@@ -335,6 +337,22 @@ class PageLoadMetricsObserver {
   // loading-dev@chromium.org if you intend to override this method.
   virtual void OnTimingUpdate(const PageLoadTiming& timing,
                               const PageLoadExtraInfo& extra_info) {}
+
+  // OnSubFrameTimingUpdate is triggered when an updated PageLoadTiming or
+  // PageLoadMetadata is available for a child frame of the current page
+  // load. The FrameTreeNodeId identifies the frame that navigation_start,
+  // child_timing, and child_metadata are associated with. The PageLoadExtraInfo
+  // contains the extra info associated with the page. navigation_start reports
+  // the time delta from the main frame navigation_start. The timings reported
+  // in child_timing are relative to the frame's navigation_start, so should be
+  // offset by navigation_start in order to get their timing relative to the
+  // main frame's navigation start.
+  virtual void OnSubFrameTimingUpdate(FrameTreeNodeId child_frame_id,
+                                      base::TimeDelta navigation_start,
+                                      const PageLoadTiming& child_timing,
+                                      const PageLoadMetadata& child_metadata,
+                                      const PageLoadExtraInfo& extra_info) {}
+
   // OnUserInput is triggered when a new user input is passed in to
   // web_contents. Contains a TimeDelta from navigation start.
   virtual void OnUserInput(const blink::WebInputEvent& event) {}