[heap] Fix context disposal heap limit

Fix two bugs:
- Initial configuration of limit allowed to go below the size of already
  allocated objects.
- Context disposal without dependend context reset the heap state to not
  configured without actually increasing the limit again.

Bug: chromium:843903
Change-Id: Ibdcf69b0b92b800f8919d5cc98186334945d811f
Reviewed-on: https://chromium-review.googlesource.com/c/1355143Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57946}

src/heap/heap.cc

@@ -1377,6 +1377,7 @@ int Heap::NotifyContextDisposed(bool dependant_context) {
   if (!dependant_context) {
     tracer()->ResetSurvivalEvents();
     old_generation_size_configured_ = false;
+    old_generation_allocation_limit_ = initial_old_generation_size_;
     MemoryReducer::Event event;
     event.type = MemoryReducer::kPossibleGarbage;
     event.time_ms = MonotonicallyIncreasingTimeInMs();
@@ -2395,7 +2396,8 @@ void Heap::UnregisterArrayBuffer(JSArrayBuffer* buffer) {
 void Heap::ConfigureInitialOldGenerationSize() {
   if (!old_generation_size_configured_ && tracer()->SurvivalEventsRecorded()) {
     old_generation_allocation_limit_ =
-        Max(heap_controller()->MinimumAllocationLimitGrowingStep(
+        Max(OldGenerationSizeOfObjects() +
+                heap_controller()->MinimumAllocationLimitGrowingStep(
                     CurrentHeapGrowingMode()),
             static_cast<size_t>(
                 static_cast<double>(old_generation_allocation_limit_) *