[Feed] Implement Content Storage API in Java

Implement Content Storage API in Java and JNI bridge.

Bug:828935

Change-Id: I6c70d18cfde0891f5c9533458bf453a891b4b2be
Reviewed-on: https://chromium-review.googlesource.com/1137739
Commit-Queue: Gang Wu <gangwu@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Reviewed-by: Filip Gorski <fgorski@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576950}
7 files changed