Reland "Avoid excessive GCs in small heaps."

Original issue's description:
> Avoid excessive GCs in small heaps.
>
> Small heaps and small heap growing factor can lead to excessive GCs in corner cases.
>
> Consider function F(old_gen_size, factor) that returns the number of bytes that
> have to be allocated in the old generation to start incremental marking.
>
> F(4MB, 1.1) = 4MB (because of kMinimumOldGenerationAllocationLimit)
> F(6MB, 1.1) = 2MB (because of kMinimumOldGenerationAllocationLimit)
> F(8MB, 1.1) = 800KB
>
> Funtion F should be monotonic in old_gen_size, but it currently has a minimum
> at kMinimumOldGenerationAllocationLimit.
>
> This CL makes F monotonic.
>
> BUG=
>
> Committed: https://crrev.com/22b1da99732b4db0754bf267ec470a2831216fb2
> Cr-Commit-Position: refs/heads/master@{#28549}

TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1148953005

Cr-Commit-Position: refs/heads/master@{#28562}

src/heap/heap.cc

@@ -5312,7 +5312,7 @@ intptr_t Heap::CalculateOldGenerationAllocationLimit(double factor,
   CHECK(factor > 1.0);
   CHECK(old_gen_size > 0);
   intptr_t limit = static_cast<intptr_t>(old_gen_size * factor);
-  limit = Max(limit, kMinimumOldGenerationAllocationLimit);
+  limit = Max(limit, old_gen_size + kMinimumOldGenerationAllocationLimit);
   limit += new_space_.Capacity();
   intptr_t halfway_to_the_max = (old_gen_size + max_old_generation_size_) / 2;
   return Min(limit, halfway_to_the_max);