Update android_system_sdk to API level 27.

Bug: 782848
No-Equivalent-Builders: true
Change-Id: I0b47af0f0c24f64811105a7d03ba8d893c443ec0
Reviewed-on: https://chromium-review.googlesource.com/795358
Commit-Queue: John Budorick <jbudorick@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#520193}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 17cfa616d9f7bc428e4525be26979bff8eb8fbd7

cipd/android/android.ensure

@@ -21,7 +21,7 @@ chromium/third_party/android_support_test_runner version:0.5-cr0
 # endless merge conflicts
 
 @Subdir third_party/android_system_sdk
-chromium/third_party/android_system_sdk version:0-cr0
+chromium/third_party/android_system_sdk version:27-cr0
 
 # Three unchanging lines
 # avoid the horror that is