Implement layout invalidation tracking in devtools

LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html

Index: LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html
diff --git a/LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html b/LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html
index af065e603608ebbbdc655e2900911c6cd595c246..281df23bdd05778eb3bdb2a9dcb417054171812b 100644
--- a/LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html
+++ b/LayoutTests/inspector/tracing/timeline-paint-with-layout-invalidations.html
@@ -51,25 +51,13 @@ function test()
 
         function testSubframe(next)
         {
-            var firstPaintRecord = InspectorTest.findFirstTimelineRecord(WebInspector.TimelineModel.RecordType.Paint);
-            var secondPaintRecord = undefined;
-
-            function findSecondPaint(record)
-            {
-                if (record.type() !== WebInspector.TimelineModel.RecordType.Paint)
-                    return false;
-                if (record === firstPaintRecord)
-                    return false;
-                secondPaintRecord = record;
-                return true;
-            }
-            InspectorTest.timelineModel().forAllRecords(findSecondPaint);
-
             // The first paint corresponds to the local frame and should have no invalidations.
+            var firstPaintRecord = InspectorTest.findFirstTimelineRecord(WebInspector.TimelineModel.RecordType.Paint);
             var firstInvalidations = firstPaintRecord._event.invalidationTrackingEvents;
             InspectorTest.assertEquals(firstInvalidations, undefined);
 
             // The second paint corresponds to the subframe and should have our layout/style invalidations.
+            var secondPaintRecord = InspectorTest.findTimelineRecord(WebInspector.TimelineModel.RecordType.Paint, 1);
             var secondInvalidations = secondPaintRecord._event.invalidationTrackingEvents;
             InspectorTest.assertEquals(secondInvalidations.length, 3);
             InspectorTest.assertEquals(secondInvalidations[0].type, WebInspector.TracingTimelineModel.RecordType.StyleRecalcInvalidationTracking);