[LCP] Browser: reuse LCP-handler for main-frame-LCP

As we already have LCP-handler since this CL
https://chromium-review.googlesource.com/c/chromium/src/+/1500254,
the main-frame-LCP can benefit from it by reusing the
LCP-handler's functions.

Bug: 940587

Change-Id: I24d2fbb6d11a50c114d767c4c87c048aaea4c167
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1517162Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686543}

chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.cc

@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+
 #include <memory>
 #include <utility>
 
@@ -46,7 +47,8 @@ PageLoadType GetPageLoadType(ui::PageTransition transition) {
 void RecordFirstMeaningfulPaintStatus(
     internal::FirstMeaningfulPaintStatus status) {
   UMA_HISTOGRAM_ENUMERATION(internal::kHistogramFirstMeaningfulPaintStatus,
-      status, internal::FIRST_MEANINGFUL_PAINT_LAST_ENTRY);
+                            status,
+                            internal::FIRST_MEANINGFUL_PAINT_LAST_ENTRY);
 }
 
 void RecordTimeToInteractiveStatus(internal::TimeToInteractiveStatus status) {
@@ -797,41 +799,50 @@ void CorePageLoadMetricsObserver::RecordTimingHistograms(
                         info.first_foreground_time.value());
   }
 
-  if (WasStartedInForegroundOptionalEventInForeground(
-          main_frame_timing.paint_timing->largest_image_paint, info)) {
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramLargestImagePaint,
-        main_frame_timing.paint_timing->largest_image_paint.value());
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_image_paint =
+          largest_contentful_paint_handler_.MainFrameLargestImagePaint();
+  if (!main_frame_largest_image_paint.IsEmpty() &&
+      WasStartedInForegroundOptionalEventInForeground(
+          main_frame_largest_image_paint.Time(), info)) {
+    PAGE_LOAD_HISTOGRAM(internal::kHistogramLargestImagePaint,
+                        main_frame_largest_image_paint.Time().value());
   }
-  if (WasStartedInForegroundOptionalEventInForeground(
-          main_frame_timing.paint_timing->largest_text_paint, info)) {
-    PAGE_LOAD_HISTOGRAM(
-        internal::kHistogramLargestTextPaint,
-        main_frame_timing.paint_timing->largest_text_paint.value());
-  }
-  base::Optional<base::TimeDelta> largest_content_paint_time;
-  uint64_t largest_content_paint_size;
-  PageLoadMetricsObserver::LargestContentType largest_content_type;
-  if (AssignTimeAndSizeForLargestContentfulPaint(
-          main_frame_timing.paint_timing, &largest_content_paint_time,
-          &largest_content_paint_size, &largest_content_type) &&
+
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_text_paint =
+          largest_contentful_paint_handler_.MainFrameLargestTextPaint();
+  if (!main_frame_largest_text_paint.IsEmpty() &&
       WasStartedInForegroundOptionalEventInForeground(
-          largest_content_paint_time, info)) {
+          main_frame_largest_text_paint.Time(), info)) {
+    PAGE_LOAD_HISTOGRAM(internal::kHistogramLargestTextPaint,
+                        main_frame_largest_text_paint.Time().value());
+  }
+
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_contentful_paint =
+          largest_contentful_paint_handler_.MainFrameLargestContentfulPaint();
+  if (!main_frame_largest_contentful_paint.IsEmpty() &&
+      WasStartedInForegroundOptionalEventInForeground(
+          main_frame_largest_contentful_paint.Time(), info)) {
     PAGE_LOAD_HISTOGRAM(internal::kHistogramLargestContentfulPaintMainFrame,
-                        largest_content_paint_time.value());
+                        main_frame_largest_contentful_paint.Time().value());
     UMA_HISTOGRAM_ENUMERATION(
         internal::kHistogramLargestContentfulPaintMainFrameContentType,
-        largest_content_type);
+        main_frame_largest_contentful_paint.Type());
   }
 
-  const page_load_metrics::ContentfulPaintTimingInfo& paint =
-      largest_contentful_paint_handler_.MergeMainFrameAndSubframes();
-  if (!paint.IsEmpty() &&
-      WasStartedInForegroundOptionalEventInForeground(paint.Time(), info)) {
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      all_frames_largest_contentful_paint =
+          largest_contentful_paint_handler_.MergeMainFrameAndSubframes();
+  if (!all_frames_largest_contentful_paint.IsEmpty() &&
+      WasStartedInForegroundOptionalEventInForeground(
+          all_frames_largest_contentful_paint.Time(), info)) {
     PAGE_LOAD_HISTOGRAM(internal::kHistogramLargestContentfulPaint,
-                        paint.Time().value());
+                        all_frames_largest_contentful_paint.Time().value());
     UMA_HISTOGRAM_ENUMERATION(
-        internal::kHistogramLargestContentfulPaintContentType, paint.Type());
+        internal::kHistogramLargestContentfulPaintContentType,
+        all_frames_largest_contentful_paint.Type());
   }
 
   if (main_frame_timing.paint_timing->first_paint &&

chrome/browser/page_load_metrics/observers/largest_contentful_paint_handler.h

@@ -78,6 +78,21 @@ class LargestContentfulPaintHandler {
     return main_frame_tree_node_id_.value();
   }
 
+  // We merge the candidates from text side and image side to get the largest
+  // candidate across both types of content.
+  const ContentfulPaintTimingInfo& MainFrameLargestContentfulPaint() {
+    return main_frame_contentful_paint_.MergeTextAndImageTiming();
+  }
+  const ContentfulPaintTimingInfo& SubframesLargestContentfulPaint() {
+    return subframe_contentful_paint_.MergeTextAndImageTiming();
+  }
+  const ContentfulPaintTimingInfo& MainFrameLargestImagePaint() {
+    return main_frame_contentful_paint_.Image();
+  }
+  const ContentfulPaintTimingInfo& MainFrameLargestTextPaint() {
+    return main_frame_contentful_paint_.Text();
+  }
+
   // We merge the candidates from main frame and subframe to get the largest
   // candidate across all frames.
   const ContentfulPaintTimingInfo& MergeMainFrameAndSubframes();

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc

@@ -298,35 +298,41 @@ void UkmPageLoadMetricsObserver::RecordTimingMetrics(
     builder.SetExperimental_PaintTiming_NavigationToFirstMeaningfulPaint(
         timing.paint_timing->first_meaningful_paint.value().InMilliseconds());
   }
-  if (timing.paint_timing->largest_image_paint.has_value() &&
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_image_paint =
+          largest_contentful_paint_handler_.MainFrameLargestImagePaint();
+  if (!main_frame_largest_image_paint.IsEmpty() &&
       WasStartedInForegroundOptionalEventInForeground(
-          timing.paint_timing->largest_image_paint, info)) {
+          main_frame_largest_image_paint.Time(), info)) {
     builder.SetExperimental_PaintTiming_NavigationToLargestImagePaint(
         timing.paint_timing->largest_image_paint.value().InMilliseconds());
   }
-  if (timing.paint_timing->largest_text_paint.has_value() &&
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_text_paint =
+          largest_contentful_paint_handler_.MainFrameLargestTextPaint();
+  if (!main_frame_largest_text_paint.IsEmpty() &&
       WasStartedInForegroundOptionalEventInForeground(
-          timing.paint_timing->largest_text_paint, info)) {
+          main_frame_largest_text_paint.Time(), info)) {
     builder.SetExperimental_PaintTiming_NavigationToLargestTextPaint(
         timing.paint_timing->largest_text_paint.value().InMilliseconds());
   }
-  base::Optional<base::TimeDelta> largest_content_paint_time;
-  uint64_t largest_content_paint_size;
-  PageLoadMetricsObserver::LargestContentType largest_content_type;
-  if (AssignTimeAndSizeForLargestContentfulPaint(
-          timing.paint_timing, &largest_content_paint_time,
-          &largest_content_paint_size, &largest_content_type) &&
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      main_frame_largest_contentful_paint =
+          largest_contentful_paint_handler_.MainFrameLargestContentfulPaint();
+  if (!main_frame_largest_contentful_paint.IsEmpty() &&
       WasStartedInForegroundOptionalEventInForeground(
-          largest_content_paint_time, info)) {
+          main_frame_largest_contentful_paint.Time(), info)) {
     builder.SetPaintTiming_NavigationToLargestContentfulPaint_MainFrame(
-        largest_content_paint_time.value().InMilliseconds());
+        main_frame_largest_contentful_paint.Time().value().InMilliseconds());
   }
-  const page_load_metrics::ContentfulPaintTimingInfo& paint =
-      largest_contentful_paint_handler_.MergeMainFrameAndSubframes();
-  if (!paint.IsEmpty() &&
-      WasStartedInForegroundOptionalEventInForeground(paint.Time(), info)) {
+  const page_load_metrics::ContentfulPaintTimingInfo&
+      all_frames_largest_contentful_paint =
+          largest_contentful_paint_handler_.MergeMainFrameAndSubframes();
+  if (!all_frames_largest_contentful_paint.IsEmpty() &&
+      WasStartedInForegroundOptionalEventInForeground(
+          all_frames_largest_contentful_paint.Time(), info)) {
     builder.SetPaintTiming_NavigationToLargestContentfulPaint(
-        paint.Time().value().InMilliseconds());
+        all_frames_largest_contentful_paint.Time().value().InMilliseconds());
   }
   if (timing.interactive_timing->interactive) {
     base::TimeDelta time_to_interactive =