spdy: push referrer call period starts when first resource is added. Before it started when main resource was created

jetty-spdy/spdy-jetty-http/src/main/java/org/eclipse/jetty/spdy/http/ReferrerPushStrategy.java

@@ -24,6 +24,7 @@ import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.regex.Pattern;
 
 import org.eclipse.jetty.spdy.api.Headers;
@@ -213,17 +214,23 @@ public class ReferrerPushStrategy implements PushStrategy
     private class MainResource
     {
         private final String name;
-        private final long created = System.nanoTime();
         private final Set<String> resources = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>());
+        private final AtomicLong firstResourceAdded = new AtomicLong(-1);
 
-        MainResource(String name)
+        private MainResource(String name)
         {
             this.name = name;
         }
 
         public boolean addResource(String url, String origin, String referrer)
         {
-            long delay = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - created);
+            // We start the push period here and not when initializing the main resource, because a browser with a
+            // prefilled cache won't request the subresources. If the browser with warmed up cache now hits the main
+            // resource after a server restart, the push period shouldn't start until the first subresource is
+            // being requested.
+            firstResourceAdded.compareAndSet(-1, System.nanoTime());
+
+            long delay = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - firstResourceAdded.get());
             if (!referrer.startsWith(origin) && !isPushOriginAllowed(origin))
             {
                 logger.debug("Skipped store of push metadata {} for {}: Origin: {} doesn't match or origin not allowed",