Revert of Suppress an uninitialized read in ThreadHeap<>::sweepNormalPages...

Revert of Suppress an uninitialized read in ThreadHeap<>::sweepNormalPages (patchset #2 of https://codereview.chromium.org/502233002/)

Reason for revert:
The fix (https://src.chromium.org/viewvc/blink?revision=180854) should be included by the Blink roll in http://crrev.com/ecb9875276ccd.

Original issue's description:
> Suppress an uninitialized read in ThreadHeap<>::sweepNormalPages
>
> BUG=407396
> NOTRY=true
> TBR=ager@chromium.org
> NOTREECHECKS=true
>
> Committed to pending queue: https://chromium.googlesource.com/chromium/src/+/8da39ba

TBR=ager@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=407396

Review URL: https://codereview.chromium.org/507833002

Cr-Commit-Position: refs/heads/master@{#291983}

tools/valgrind/drmemory/suppressions_full.txt

@@ -2236,9 +2236,3 @@ content.dll!content::WebContentsImpl::CreateRenderViewForRenderManager
 content.dll!content::NavigationControllerImpl::LoadEntry
 ...
 *!extensions::ExtensionHost::LoadInitialURL
-
-UNINITIALIZED READ
-name=bug_407396
-blink_platform.dll!blink::ThreadHeap<>::sweepNormalPages
-blink_platform.dll!blink::ThreadHeap<>::sweep
-blink_platform.dll!blink::ThreadState::performPendingSweep