[heap] Minor MC: Pause concurrent marking

Bug: 
Change-Id: I4e105a3a09fe3b58255189bb89fa38224078ae5c
Reviewed-on: https://chromium-review.googlesource.com/817196Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49960}

src/heap/heap.cc

@@ -1773,6 +1773,7 @@ void Heap::MinorMarkCompact() {
   IncrementalMarking::PauseBlackAllocationScope pause_black_allocation(
       incremental_marking());
   CodeSpaceMemoryModificationScope code_modifcation(this);
+  ConcurrentMarking::PauseScope pause_scope(concurrent_marking());
 
   minor_mark_compact_collector()->CollectGarbage();
 

test/cctest/cctest.status

@@ -385,10 +385,4 @@
   'test-dtoa/*': [SKIP],
 }],  # variant == wasm_traps
 
-##############################################################################
-['variant == minor_mc', {
-  # TODO(mlippautz) Flaky unreachable code crash.
-  'test-heap/GCFlags': [SKIP],
-}],  # variant == minor_mc
-
 ]

test/debugger/debugger.status

@@ -92,10 +92,4 @@
   'debug/debug-liveedit-restart-frame': [SKIP],
 }],  # 'arch == s390 or arch == s390x'
 
-##############################################################################
-['variant == minor_mc', {
-  # TODO(mlippautz) Flaky unreachable code crash.
-  'regress/regress-2318': [SKIP],
-}],  # variant == minor_mc
-
 ]