Mark http/tests/misc/performance-memory.html flaky

TBR=npm@chromium.org

BUG: 834446
Change-Id: Ia4315e380833ba43908dddd17a1f67125445b2ab
Reviewed-on: https://chromium-review.googlesource.com/1017816Reviewed-by: Majid Valipour <majidvp@chromium.org>
Commit-Queue: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551857}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4107,3 +4107,5 @@ crbug.com/833655 [ Linux ] media/controls/closed-captions-dynamic-update.html [
 crbug.com/833655 [ Linux ] virtual/new-remote-playback-pipeline/media/controls/closed-captions-dynamic-update.html [ Skip ]
 crbug.com/833658 [ Linux Win Mac ] media/video-controls-focus-movement-on-hide.html [ Pass Failure ]
 crbug.com/833100 [ Mac ] external/wpt/battery-status/battery-full-manual.https.html [ Failure ]
+
+crbug.com/834446 [ Linux ] http/tests/misc/performance-memory.html [ Pass Failure ]
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