Deflake http/tests/inspector/tracing/timeline-receive-response-event.html

As a follow-up for [1], this CL fixes the flakiness of
timeline-receive-response-event.html by dumping only the first
ResourceReceivedData event for each request.

1: https://crrev.com/48f3e047d17e5f78543bb0bec1c421ba3a69cb79

BUG=666217

Review-Url: https://codereview.chromium.org/2563613004
Cr-Commit-Position: refs/heads/master@{#437810}

third_party/WebKit/LayoutTests/http/tests/inspector/tracing/timeline-receive-response-event-expected.txt

@@ -3,14 +3,12 @@ Tests the Timeline API instrumentation of a SendRequest, ReceiveResponse etc.
         ResourceSendRequest
 ResourceReceiveResponse
 ResourceReceivedData
-ResourceReceivedData
 ResourceFinish
 EventDispatch
     FunctionCall
         ResourceSendRequest
 ResourceReceiveResponse
 ResourceReceivedData
-ResourceReceivedData
 ResourceFinish
 EventDispatch
     FunctionCall

third_party/WebKit/LayoutTests/http/tests/inspector/tracing/timeline-receive-response-event.html

@@ -33,12 +33,21 @@ function test()
         var recordTypes = TimelineModel.TimelineModel.RecordType;
         var typesToDump = new Set([recordTypes.ResourceSendRequest, recordTypes.ResourceReceiveResponse, recordTypes.ResourceReceivedData, recordTypes.ResourceFinish,
             recordTypes.EventDispatch, recordTypes.FunctionCall]);
+        let hasAlreadyDumptReceivedDataFor = new Map();
         function dumpEvent(traceEvent, level)
         {
             // Ignore stray paint & rendering events for better stability.
             var categoryName = Timeline.TimelineUIUtils.eventStyle(traceEvent).category.name;
             if (categoryName !== "loading" && categoryName !== "scripting")
                 return;
+            if (traceEvent.name === 'ResourceReceivedData') {
+                const requestId = traceEvent.args['data']['requestId'];
+                // Dump only the first ResourceReceivedData for a request for stability.
+                if (hasAlreadyDumptReceivedDataFor[requestId])
+                    return;
+                hasAlreadyDumptReceivedDataFor[requestId] = true;
+            }
+
             // Here and below: pretend coalesced record are just not there, as coalescation is time dependent and, hence, not stable.
             // Filter out InjectedScript function call because they happen out of sync.
             if (typesToDump.has(traceEvent.name) && (traceEvent.name !== "FunctionCall" || traceEvent.args["data"]["url"]))