Add workerStart attribute to ResourceTiming

Source/core/timing/PerformanceResourceTiming.cpp

Index: Source/core/timing/PerformanceResourceTiming.cpp
diff --git a/Source/core/timing/PerformanceResourceTiming.cpp b/Source/core/timing/PerformanceResourceTiming.cpp
index 222edbf61957c6c7858f897b9572e5c7e2344f8b..cf0bc1be8023c46e3d1b18ed85ca94cdae284720 100644
--- a/Source/core/timing/PerformanceResourceTiming.cpp
+++ b/Source/core/timing/PerformanceResourceTiming.cpp
@@ -69,11 +69,22 @@ AtomicString PerformanceResourceTiming::initiatorType() const
     return m_initiatorType;
 }
 
+double PerformanceResourceTiming::workerStart() const
+{
+    if (!m_timing || m_timing->workerStart() == 0.0)
+        return 0.0;
+
+    return monotonicTimeToDocumentMilliseconds(m_requestingDocument.get(), m_timing->workerStart());
+}
+
 double PerformanceResourceTiming::redirectStart() const
 {
     if (!m_lastRedirectEndTime || !m_allowRedirectDetails)
         return 0.0;
 
+    if (double workerStartTime = workerStart())
+        return workerStartTime;
+
     return PerformanceEntry::startTime();
 }
 
@@ -94,6 +105,9 @@ double PerformanceResourceTiming::fetchStart() const
         return monotonicTimeToDocumentMilliseconds(m_requestingDocument.get(), m_timing->requestTime());
     }
 
+    if (double workerStartTime = workerStart())
+        return workerStartTime;
+
     return PerformanceEntry::startTime();
 }