Merge pull request #187 from w3c/dropped-entries-count

Update dropped entries count processing logic

index.html

@@ -365,6 +365,7 @@ <h2>The <dfn>PerformanceObserver</dfn> interface</h2>
       </li>
       <li>A <code>DOMString</code> <dfn>observer type</dfn> which is initially
       <code>"undefined"</code>.</li>
+      <li>A boolean <dfn>requires dropped entries</dfn> which is initially set to false.</li>
     </ul>
     <p>The `PerformanceObserver(callback)` constructor must create a new
     <a>PerformanceObserver</a> object with its <a>observer callback</a>
@@ -403,7 +404,8 @@ <h2><dfn>PerformanceObserverCallbackOptions</dfn> dictionary</h2>
       <dl>
         <dt><dfn>droppedEntriesCount</dfn></dt>
         <dd>An integer representing the dropped entries count for the entry types that the
-        observer is observing when its callback is run.</dd>
+        observer is observing when the <a>PerformanceObserver</a>'s <a>requires dropped entries</a>
+        is set.</dd>
       </dl>
 </section>
     <section>
@@ -448,6 +450,7 @@ <h2><dfn>observe()</dfn> method</h2>
             </li>
           </ol>
         </li>
+        <li>Set <a>this</a>'s <a>requires dropped entries</a> to true.</li>
         <li>If <a>this</a>'s <a>observer type</a> is
         <code>"multiple"</code>, run the following steps:
           <ol>
@@ -753,28 +756,36 @@ <h2>Queue the PerformanceObserver task</h2>
                 {{PerformanceObserverEntryList}}, with its <a>entry list</a> set
                 to <var>entries</var>.
                 </li>
-                <li>Let <var>droppedEntriesCount</var> be 0.</li>
-                <li>For each <a>PerformanceObserverInit</a> <var>item</var> in
-                <var>registeredObserver</var>'s <a>options list</a>:
+                <li>Let <var>droppedEntriesCount</var> be null.</li>
+                <li>If <var>po</var>'s <a>requires dropped entries</a> is set, perform the following
+                steps:
                   <ol>
-                    <li>For each <a data-cite="WEBIDL#idl-DOMString">DOMString</a>
-                    <var>entryType</var> that appears either as <var>item</var>'s <a data-link-for=
-                    "PerformanceObserverInit">type</a> or in <var>item</var>'s
-                    <a data-link-for="PerformanceObserverInit">entryTypes</a>:
-                      <ol>
-                        <li>Let <var>map</var> be <var>relevantGlobal</var>'s <a>performance entry
-                        buffer map</a>.</li>
-                        <li>Let <var>tuple</var> be the result of <a>getting the value of entry</a>
-                        on <var>map</var> given <var>entryType</var> as <a>key</a>.</li>
-                        <li>Increase <var>droppedEntriesCount</var> by <var>tuple</var>'s
-                        <a>dropped entries count</a>.</li>
-                      </ol>
+                    <li>Set <var>droppedEntriesCount</var> to 0.</li>
+                    <li>For each <a>PerformanceObserverInit</a> <var>item</var> in
+                    <var>registeredObserver</var>'s <a>options list</a>:
+                    <ol>
+                      <li>For each <a data-cite="WEBIDL#idl-DOMString">DOMString</a>
+                      <var>entryType</var> that appears either as <var>item</var>'s <a data-link-for=
+                      "PerformanceObserverInit">type</a> or in <var>item</var>'s
+                      <a data-link-for="PerformanceObserverInit">entryTypes</a>:
+                        <ol>
+                          <li>Let <var>map</var> be <var>relevantGlobal</var>'s <a>performance entry
+                          buffer map</a>.</li>
+                          <li>Let <var>tuple</var> be the result of <a>getting the value of entry</a>
+                          on <var>map</var> given <var>entryType</var> as <a>key</a>.</li>
+                          <li>Increase <var>droppedEntriesCount</var> by <var>tuple</var>'s
+                          <a>dropped entries count</a>.</li>
+                        </ol>
+                      </li>
+                    </ol>
                     </li>
+                    <li>Set <var>po</var>'s <a>requires dropped entries</a> to false.</li>
                   </ol>
                 </li>
                 <li>Let <var>callbackOptions</var> be a <a>PerformanceObserverCallbackOptions</a>
                 with its <a data-link-for="PerformanceObserverCallbackOptions">droppedEntriesCount</a>
-                set to <var>droppedEntriesCount</var>.</li>
+                set to <var>droppedEntriesCount</var> if <var>droppedEntriesCount</var> is not null,
+                otherwise unset.</li>
                 <li>Call <var>po</var>’s <a>observer callback</a> with
                 <var>observerEntryList</var> as the first argument, with <var>po</var>
                 as the second argument and as <a>callback this value</a>, and with