Revert "[oilpan] Fix for EsimateLiveSize"

This reverts commit aceb7d67.

Reason for revert: Even though the heuristic seems off we tuned parameters around it that will trigger GCs. 

Bug: 852413

Original change's description:
> [oilpan] Fix for EsimateLiveSize
> 
> Take current value for base size, similarly to what is used for
> PartitionAlloc. This makes sure that an esimate is computed at the time
> of calling the method.
> 
> Bug: chromium:840789
> Change-Id: Iab7e63f5395cbc74226cd786d420c6145fdb7dd9
> Reviewed-on: https://chromium-review.googlesource.com/1094822
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Reviewed-by: Keishi Hattori <keishi@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#565967}

TBR=haraken@chromium.org,keishi@chromium.org,hpayer@chromium.org,mlippautz@chromium.org

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

Bug: chromium:840789
Change-Id: I323527b2f6d4703773ca11f980a4233cb8554f7a
Reviewed-on: https://chromium-review.googlesource.com/1100435Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567131}

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

@@ -394,30 +394,30 @@ size_t ThreadState::TotalMemorySize() {
 }
 
 size_t ThreadState::EstimatedLiveSize(size_t estimation_base_size,
-                                      size_t size_at_prev_gc) {
+                                      size_t size_at_last_gc) {
   const ThreadHeapStatsCollector& stats_collector = *heap_->stats_collector();
   const ThreadHeapStatsCollector::Event& prev = stats_collector.previous();
 
   if (prev.wrapper_count_before_sweeping == 0)
     return estimation_base_size;
 
-  // (estimated size) = (estimation base size) -
-  //     (heap size at the last GC) *
-  //     (# of persistent handles collected since the last GC) /
-  //     (# of persistent handles at the last GC)
-  size_t size_freed_by_collecting_persistents =
-      static_cast<size_t>(static_cast<double>(size_at_prev_gc) *
-                          stats_collector.collected_wrapper_count() /
-                          prev.wrapper_count_before_sweeping);
-  if (estimation_base_size < size_freed_by_collecting_persistents)
+  // (estimated size) = (estimation base size) - (heap size at the last GC) /
+  //   (# of persistent handles at the last GC) *
+  //     (# of persistent handles collected since the last GC)
+  size_t size_retained_by_collected_persistents = static_cast<size_t>(
+      1.0 * size_at_last_gc / prev.wrapper_count_before_sweeping *
+      stats_collector.collected_wrapper_count());
+  if (estimation_base_size < size_retained_by_collected_persistents)
     return 0;
-  return estimation_base_size - size_freed_by_collecting_persistents;
+  return estimation_base_size - size_retained_by_collected_persistents;
 }
 
 double ThreadState::HeapGrowingRate() {
   const size_t current_size = heap_->stats_collector()->object_size_in_bytes();
-  const size_t estimated_size = EstimatedLiveSize(
-      current_size, heap_->stats_collector()->previous().marked_bytes);
+  // TODO(mlippautz): Clarify those two parameters below.
+  const size_t estimated_size =
+      EstimatedLiveSize(heap_->stats_collector()->previous().marked_bytes,
+                        heap_->stats_collector()->previous().marked_bytes);
 
   // If the estimatedSize is 0, we set a high growing rate to trigger a GC.
   double growing_rate =

third_party/blink/renderer/platform/heap/thread_state.h

@@ -649,15 +649,7 @@ class PLATFORM_EXPORT ThreadState {
   // conservative GC was performed to handle the emergency.
   bool ForceMemoryPressureGCIfNeeded();
 
-  // Esimates the size of a heap based on |size_at_prev_gc| and wrapper counts
-  // (live and collected). |current_size| should be the currently allocated size
-  // for that heap.
-  //
-  // Note that this function should not be called while sweeping is running as
-  // it uses snapshots and live values collected during garbage collection and
-  // calling it during sweeping mixes garbage collection cycles.
-  size_t EstimatedLiveSize(size_t current_size, size_t size_at_prev_gc);
-
+  size_t EstimatedLiveSize(size_t current_size, size_t size_at_last_gc);
   size_t TotalMemorySize();
   double HeapGrowingRate();
   double PartitionAllocGrowingRate();