Support counter graphs in Timeline based on trace events

Source/devtools/front_end/timeline/TimelineMemoryOverview.js

Index: Source/devtools/front_end/timeline/TimelineMemoryOverview.js
diff --git a/Source/devtools/front_end/timeline/TimelineMemoryOverview.js b/Source/devtools/front_end/timeline/TimelineMemoryOverview.js
index c00107b26dbc0d95aa8341867e69feb54db229bf..17f2fc0d6c898a6735abe10ab1b1690c58a05e14 100644
--- a/Source/devtools/front_end/timeline/TimelineMemoryOverview.js
+++ b/Source/devtools/front_end/timeline/TimelineMemoryOverview.js
@@ -68,10 +68,8 @@ WebInspector.TimelineMemoryOverview.prototype = {
          */
         function calculateMinMaxSizes(record)
         {
-            if (record.type() !== WebInspector.TimelineModel.RecordType.UpdateCounters)
-                return;
-            var counters = record.data();
-            if (!counters.jsHeapSizeUsed)
+            var counters = record.counters();
+            if (!counters || !counters.jsHeapSizeUsed)
                 return;
             maxUsedHeapSize = Math.max(maxUsedHeapSize, counters.jsHeapSizeUsed);
             minUsedHeapSize = Math.min(minUsedHeapSize, counters.jsHeapSizeUsed);
@@ -92,10 +90,8 @@ WebInspector.TimelineMemoryOverview.prototype = {
          */
         function buildHistogram(record)
         {
-            if (record.type() !== WebInspector.TimelineModel.RecordType.UpdateCounters)
-                return;
-            var counters = record.data();
-            if (!counters.jsHeapSizeUsed)
+            var counters = record.counters();
+            if (!counters || !counters.jsHeapSizeUsed)
                 return;
             var x = Math.round((record.endTime() - minTime) * xFactor);
             var y = Math.round((counters.jsHeapSizeUsed - minUsedHeapSize) * yFactor);