Disable HeapThreadDeathTest.PersistentSameThreadCheck on Linux

This test may timeout on Linux:
https://analysis.chromium.org/p/chromium/flake-portal/flakes/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVyVgsSBUZsYWtlIktjaHJvbWl1bUBibGlua19oZWFwX3VuaXR0ZXN0c0BIZWFwVGhyZWFkRGVhdGhUZXN0LlBlcnNpc3RlbnRTYW1lVGhyZWFkQ2hlY2sM

TBR=bikineev@chromium.org

Bug: 1043580
Change-Id: Iba18b7c7f6c57c65ef285397198d2a12e2d19951
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2025975Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736125}

third_party/blink/renderer/platform/heap/heap_thread_test.cc

@@ -162,7 +162,8 @@ class PersistentSameThreadCheckTester : public AlternatingThreadTester {
 #if DCHECK_IS_ON()
 // TODO(keishi) This test is flaky on mac-rel bot.
 // crbug.com/709069
-#if !defined(OS_MACOSX)
+// This test is also flaky on Linux. crbug.com/1043580.
+#if !defined(OS_MACOSX) && !defined(OS_LINUX)
 TEST_F(HeapThreadDeathTest, PersistentSameThreadCheck) {
   EXPECT_DEATH(PersistentSameThreadCheckTester().Test(), "");
 }