Drop prebuilt files to android source tree.

The following files have been updated as part of this change:

current/Android.bp
current/snapshot-creation-build-number.txt
current/licenses/build/soong/licenses/LICENSE
current/hiddenapi/annotation-flags.csv
current/hiddenapi/filtered-flags.csv
current/hiddenapi/filtered-stub-flags.csv
current/hiddenapi/index.csv
current/hiddenapi/metadata.csv
current/hiddenapi/signature-patterns.csv
current/sdk_library/system/framework-sdkextensions-removed.txt
current/sdk_library/system/framework-sdkextensions-stubs.jar
current/sdk_library/system/framework-sdkextensions.srcjar
current/sdk_library/system/framework-sdkextensions.txt
current/sdk_library/system/framework-sdkextensions_annotations.zip
current/sdk_library/module-lib/framework-sdkextensions-removed.txt
current/sdk_library/module-lib/framework-sdkextensions-stubs.jar
current/sdk_library/module-lib/framework-sdkextensions.srcjar
current/sdk_library/module-lib/framework-sdkextensions.txt
current/sdk_library/module-lib/framework-sdkextensions_annotations.zip
current/sdk_library/public/framework-sdkextensions-removed.txt
current/sdk_library/public/framework-sdkextensions-stubs.jar
current/sdk_library/public/framework-sdkextensions.srcjar
current/sdk_library/public/framework-sdkextensions.txt
current/sdk_library/public/framework-sdkextensions_annotations.zip

Built here: ab/10917791

This build IS suitable for public release.

The change is generated with prebuilt drop tool.

Test: presubmit
Change-Id: Iffdedfc5d81d8efcb1f67b356d66a74c6c87e8ba