am 143e6109: DO NOT MERGE Clarify the explanation of Android\'s security design.

Merge commit '143e61097e3aa2f6fd2951c707f35c35d3be25e3' into gingerbread-plus-aosp

* commit '143e61097e3aa2f6fd2951c707f35c35d3be25e3':
  DO NOT MERGE Clarify the explanation of Android's security design.