[LargestContentfulPaint] Set startTime

Currently startTime is 0, which is a problem because getEntries()
methods all sort by startTime. To help with this problem, we set the
startTime to renderTime, if available, or to loadTime, if renderTime is
nt available.

Bug: 965505
Change-Id: Ie70b69269f7ce4be0fdc94f33a44a84e062d3ba5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1719379Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681147}

third_party/blink/renderer/core/timing/largest_contentful_paint.cc

@@ -10,13 +10,14 @@
 
 namespace blink {
 
-LargestContentfulPaint::LargestContentfulPaint(double render_time,
+LargestContentfulPaint::LargestContentfulPaint(double start_time,
+                                               double render_time,
                                                uint64_t size,
                                                double load_time,
                                                const AtomicString& id,
                                                const String& url,
                                                Element* element)
-    : PerformanceEntry(g_empty_atom, 0, 0),
+    : PerformanceEntry(g_empty_atom, start_time, start_time),
       size_(size),
       render_time_(render_time),
       load_time_(load_time),

third_party/blink/renderer/core/timing/largest_contentful_paint.h

@@ -17,7 +17,8 @@ class CORE_EXPORT LargestContentfulPaint final : public PerformanceEntry {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
-  LargestContentfulPaint(double render_time,
+  LargestContentfulPaint(double start_time,
+                         double render_time,
                          uint64_t size,
                          double load_time,
                          const AtomicString& id,

third_party/blink/renderer/core/timing/window_performance.cc

@@ -446,9 +446,13 @@ void WindowPerformance::OnLargestContentfulPaintUpdated(
     const AtomicString& id,
     const String& url,
     Element* element) {
+  double render_timestamp = MonotonicTimeToDOMHighResTimeStamp(paint_time);
+  double load_timestamp = MonotonicTimeToDOMHighResTimeStamp(load_time);
+  double start_timestamp =
+      render_timestamp != 0.0 ? render_timestamp : load_timestamp;
   auto* entry = MakeGarbageCollected<LargestContentfulPaint>(
-      MonotonicTimeToDOMHighResTimeStamp(paint_time), paint_size,
-      MonotonicTimeToDOMHighResTimeStamp(load_time), id, url, element);
+      start_timestamp, render_timestamp, paint_size, load_timestamp, id, url,
+      element);
   if (HasObserverFor(PerformanceEntry::kLargestContentfulPaint))
     NotifyObserversOfEntry(*entry);
   AddLargestContentfulPaint(entry);

third_party/blink/web_tests/external/wpt/largest-contentful-paint/contracted-image.html

@@ -25,7 +25,7 @@
           'The rendering timestamp should occur after script starts running.');
         assert_greater_than_equal(performance.now(), entry.renderTime,
           'The rendering timestamp should occur before the entry is dispatched to the observer.');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         // black-rectangle.png is 100 x 50. It occupies 50 x 50 so size will be bounded by the displayed size.
         assert_equals(entry.size, 2500);

third_party/blink/web_tests/external/wpt/largest-contentful-paint/cross-origin-image.sub.html

@@ -16,7 +16,7 @@
         const entry = entryList.getEntries()[0];
         assert_equals(entry.entryType, 'largest-contentful-paint');
         assert_equals(entry.renderTime, 0, 'The renderTime value should be 0 for a cross origin image.');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.loadTime, 'startTime should equal loadTime');
         assert_equals(entry.duration, 0);
         // blue.png is 133 x 106.
         assert_equals(entry.size, 14098);

third_party/blink/web_tests/external/wpt/largest-contentful-paint/expanded-image.html

@@ -25,7 +25,7 @@
           'The rendering timestamp should occur after script starts running.');
         assert_greater_than_equal(performance.now(), entry.renderTime,
           'The rendering timestamp should occur before the entry is dispatched to the observer.');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         // black-rectangle.png is 100 x 50. It occupies 300 x 300 so size will be bounded by the intrinsic size.
         assert_equals(entry.size, 5000);

third_party/blink/web_tests/external/wpt/largest-contentful-paint/image-src-change.html

@@ -21,7 +21,7 @@
           'The rendering timestamp should occur after script starts running.');
         assert_greater_than_equal(performance.now(), entry.renderTime,
           'The rendering timestamp should occur before the entry is dispatched to the observer.');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         if (firstCallback) {
           // blue.png is 133 x 106.

third_party/blink/web_tests/external/wpt/largest-contentful-paint/loadTime-after-appendChild.html

@@ -15,7 +15,7 @@
         assert_equals(entryList.getEntries().length, 1);
         const entry = entryList.getEntries()[0];
         assert_equals(entry.entryType, 'largest-contentful-paint');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         assert_equals(entry.url, window.location.origin + '/images/black-rectangle.png');
         assert_greater_than(entry.renderTime, entry.loadTime,

third_party/blink/web_tests/external/wpt/largest-contentful-paint/observe-image.html

@@ -19,7 +19,7 @@
           'The rendering timestamp should occur after script starts running.');
         assert_greater_than_equal(performance.now(), entry.renderTime,
           'The rendering timestamp should occur before the entry is dispatched to the observer.');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         // blue.png is 133 x 106.
         assert_equals(entry.size, 14098);

third_party/blink/web_tests/external/wpt/largest-contentful-paint/observe-text.html

@@ -22,7 +22,7 @@ p {
         assert_equals(entry.entryType, 'largest-contentful-paint');
         assert_greater_than_equal(entry.renderTime, beforeRender);
         assert_greater_than_equal(performance.now(), entry.renderTime);
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         // Some lower bound: height of at least 12 px.
         // Width of at least 100 px.

third_party/blink/web_tests/external/wpt/largest-contentful-paint/repeated-image.html

@@ -24,7 +24,7 @@
         assert_equals(entryList.getEntries().length, 1);
         const entry = entryList.getEntries()[0];
         assert_equals(entry.entryType, 'largest-contentful-paint');
-        assert_equals(entry.startTime, 0);
+        assert_equals(entry.startTime, entry.renderTime, 'startTime should equal renderTime');
         assert_equals(entry.duration, 0);
         assert_equals(entry.url, path);
         assert_less_than(entry.renderTime, performance.now(),