Improved and generalized page load metric immediate event logging.

components/page_load_metrics/browser/metrics_web_contents_observer.cc

 // 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.
 
 #include "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 
 #include <algorithm>
 #include <string>
 #include <utility>
 
@@ skipping 185 matching lines @@
   return ABORT_OTHER;
 }
 
 void LogAbortChainSameURLHistogram(int aborted_chain_size_same_url) {
   if (aborted_chain_size_same_url > 0) {
     UMA_HISTOGRAM_COUNTS(internal::kAbortChainSizeSameURL,
                          aborted_chain_size_same_url);
   }
 }
 
+void DispatchObserverTimingCallbacks(PageLoadMetricsObserver* observer,
+                                     const PageLoadTiming& last_timing,
+                                     const PageLoadTiming& new_timing,
+                                     const PageLoadExtraInfo& extra_info) {
+  observer->OnTimingUpdate(new_timing, extra_info);
+  if (!new_timing.dom_content_loaded_event_start.is_zero() &&
+      last_timing.dom_content_loaded_event_start.is_zero())
+    observer->OnDomContentLoadedEventStart(new_timing, extra_info);
+  if (!new_timing.load_event_start.is_zero() &&
+      last_timing.load_event_start.is_zero())
+    observer->OnLoadEventStart(new_timing, extra_info);
+  if (!new_timing.first_layout.is_zero() && last_timing.first_layout.is_zero())
+    observer->OnFirstLayout(new_timing, extra_info);
+  if (!new_timing.first_paint.is_zero() && last_timing.first_paint.is_zero())
+    observer->OnFirstPaint(new_timing, extra_info);
+  if (!new_timing.first_text_paint.is_zero() &&
+      last_timing.first_text_paint.is_zero())
+    observer->OnFirstTextPaint(new_timing, extra_info);
+  if (!new_timing.first_image_paint.is_zero() &&
+      last_timing.first_image_paint.is_zero())
+    observer->OnFirstImagePaint(new_timing, extra_info);
+  if (!new_timing.first_contentful_paint.is_zero() &&
+      last_timing.first_contentful_paint.is_zero())
+    observer->OnFirstContentfulPaint(new_timing, extra_info);
+  if (!new_timing.parse_start.is_zero() && last_timing.parse_start.is_zero())
+    observer->OnParseStart(new_timing, extra_info);
+  if (!new_timing.parse_stop.is_zero() && last_timing.parse_stop.is_zero())
+    observer->OnParseStop(new_timing, extra_info);
+}
+
 }  // namespace
 
 PageLoadTracker::PageLoadTracker(
     bool in_foreground,
     PageLoadMetricsEmbedderInterface* embedder_interface,
     const GURL& currently_committed_url,
     content::NavigationHandle* navigation_handle,
     int aborted_chain_size,
     int aborted_chain_size_same_url)
     : renderer_tracked_(false),
@@ skipping 127 matching lines @@
   // different start time from an earlier struct is considered invalid.
   bool valid_timing_descendent =
       timing_.navigation_start.is_null() ||
       timing_.navigation_start == new_timing.navigation_start;
   // Ensure flags sent previously are still present in the new metadata fields.
   bool valid_behavior_descendent =
       (metadata_.behavior_flags & new_metadata.behavior_flags) ==
       metadata_.behavior_flags;
   if (IsValidPageLoadTiming(new_timing) && valid_timing_descendent &&
       valid_behavior_descendent) {
+    // There are some subtle ordering constraints here. GetPageLoadMetricsInfo()
+    // must be called before DispatchObserverTimingCallbacks, but its
+    // implementation depends on the state of metadata_, so we need to update
+    // metadata_ before calling GetPageLoadMetricsInfo. Thus, we make a copy of
+    // timing here, update timing_ and metadata_, and then proceed to dispatch
+    // the observer timing callbacks.
+    const PageLoadTiming last_timing = timing_;
     timing_ = new_timing;
     metadata_ = new_metadata;
     const PageLoadExtraInfo info = GetPageLoadMetricsInfo();
     for (const auto& observer : observers_) {
-      observer->OnTimingUpdate(timing_, info);
+      DispatchObserverTimingCallbacks(observer.get(), last_timing, new_timing,
+                                      info);
     }
     return true;
   }
   return false;
 }
 
 void PageLoadTracker::set_renderer_tracked(bool renderer_tracked) {
   renderer_tracked_ = renderer_tracked;
 }
 
@@ skipping 375 matching lines @@
 
   if (!committed_load_->UpdateTiming(timing, metadata)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).
     // We expect this to be a rare occurrence.
     RecordInternalError(ERR_BAD_TIMING_IPC);
   }
 }
 
 }  // namespace page_load_metrics