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This CL adds the skeleton of chrome cart service which will later be
used to read, write and maintain data of chrome cart module. This CL
also adds a singleton CartServiceFactory to acquire CartService.

Bug: 1157892
Change-Id: Ia4bde1bc514cf83fe445f8c8be24b093b05fb0b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2597813
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839158}