Self-install Android SDK/NDK tools on each build.

This mechanism was enabled for the FYI bot a week ago and looks good.

BUG=None
TEST=

Review URL: https://chromiumcodereview.appspot.com/9429073

git-svn-id: http://src.chromium.org/svn/trunk/src/build@124048 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/buildbot_main.sh

@@ -14,5 +14,6 @@ ROOT=$(cd "$(dirname $0)"; pwd)
 ## bb_force_bot_green_and_exit
 
 bb_baseline_setup "${ROOT}"/../..
+bb_install_build_deps "${ROOT}"/../..
 bb_compile
 

android/buildbot_try_compile.sh

@@ -13,4 +13,5 @@ ROOT=$(cd "$(dirname $0)"; pwd)
 ## bb_force_bot_green_and_exit
 
 bb_baseline_setup "${ROOT}"/../..
+bb_install_build_deps "${ROOT}"/../..
 bb_compile

android/buildbot_try_compile_test.sh

@@ -13,5 +13,6 @@ ROOT=$(cd "$(dirname $0)"; pwd)
 ## bb_force_bot_green_and_exit
 
 bb_baseline_setup "${ROOT}"/../..
+bb_install_build_deps "${ROOT}"/../..
 bb_compile
 bb_run_tests