message: significantly reduce the size of the per-sizeclass thread-local caches
  This causes us to balloon memory usage under Firefox from ~ 530 MB to
  over 700 MB.
diff: @@ -77,8 +77,8 @@ static constexpr uint32_t kMinArenaExpansion = 4096; // 16 MB in pages
  // ensures we amortize the cost of going to the global heap enough
  static constexpr uint32_t kMinStringLen = 8;
  -static constexpr size_t kMiniheapRefillGoalSize = 256 * 1024;
  -static constexpr size_t kMaxMiniheapsPerShuffleVector = 32;
  +static constexpr size_t kMiniheapRefillGoalSize = 4 * 1024;
  +static constexpr size_t kMaxMiniheapsPerShuffleVector = 8;
  // shuffle vector features
  static constexpr int16_t kMaxShuffleVectorLength = 256; // sizeof(uint8_t) << 8
  