Revert "Reland "heap: Enable concurrent sweeping""

This reverts commit 21505f63.

Reason for revert: Broke all webview perf bots

Original change's description:
> Reland "heap: Enable concurrent sweeping"
> 
> This relands 51bb0bd3 as flaky failures in webgl tests were caused by
> aecfa837.
> 
> Bug: 967258
> Change-Id: Icf2e5d050e763e112471f5ac1897a3e24f6c9006
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1713525
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Anton Bikineev <bikineev@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#679918}

TBR=haraken@chromium.org,mlippautz@chromium.org,bikineev@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 967258
Change-Id: Iff6d2058bbe0370f4cd8cae676919572f946e47e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724509Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Juan Antonio Navarro Pérez <perezju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681802}

third_party/blink/common/features.cc

@@ -313,7 +313,7 @@ const base::Feature kBlinkHeapConcurrentMarking{
     "BlinkHeapConcurrentMarking", base::FEATURE_DISABLED_BY_DEFAULT};
 // Enables concurrently sweeping Blink's heap.
 const base::Feature kBlinkHeapConcurrentSweeping{
-    "BlinkHeapConcurrentSweeping", base::FEATURE_ENABLED_BY_DEFAULT};
+    "BlinkHeapConcurrentSweeping", base::FEATURE_DISABLED_BY_DEFAULT};
 // Enables incrementally marking Blink's heap.
 const base::Feature kBlinkHeapIncrementalMarking{
     "BlinkHeapIncrementalMarking", base::FEATURE_ENABLED_BY_DEFAULT};