Enable Python auto-formatting for //build/android

This will cause presubmit to fail for deltas that don't match
YAPF rules, and also enable "git cl format" to fix any such
violations.

Bug: 846432
Change-Id: I3602e41811474a068f4780628601a14565320db9
Reviewed-on: https://chromium-review.googlesource.com/c/1364338
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#614237}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5caba8d74f3d888c65d18d45f3608ae2118c71fd

android/.style.yapf

@@ -0,0 +1,6 @@
+[style]
+based_on_style = pep8
+column_limit = 80
+blank_line_before_nested_class_or_def = true
+blank_line_before_module_docstring = true
+indent_width = 2