added gson 2.2.4 to prebuilts. DO NOT MERGE. (cherry-pick from a4be1eb295c6691f95707d3eb675065f3f209196) (cherry picked from commit 72057806235a15c0f0dbe32e25dd09cdefb6c10b) Change-Id: I59440a5b66376a4a1123ac5318c9db8b4ef9bf26