am 2c81bdc3: Cherry pick new concurrent gc trigger change from dalvik-dev.

Merge commit '2c81bdc3bb892d7d60855e14f61854f20a9f6cb8' into gingerbread-plus-aosp

* commit '2c81bdc3bb892d7d60855e14f61854f20a9f6cb8':
  Cherry pick new concurrent gc trigger change from dalvik-dev.