Use real revision mapping in bot_update module

scripts/slave/recipe_modules/android/example.expected/basic.json

Index: scripts/slave/recipe_modules/android/example.expected/basic.json
diff --git a/scripts/slave/recipe_modules/android/example.expected/basic.json b/scripts/slave/recipe_modules/android/example.expected/basic.json
index 58a58903db4d78f19561863224212ef6b1b57710..6e3b9063c64f0fe0d8f4e5d5ff0313a1b80f9a91 100644
--- a/scripts/slave/recipe_modules/android/example.expected/basic.json
+++ b/scripts/slave/recipe_modules/android/example.expected/basic.json
@@ -13,6 +13,8 @@
       "totallyanandroid-m1",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'svn://svn-mirror.golo.chromium.org/blink/trunk'}, 'deps_file': '', 'managed': True, 'name': 'src', 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}]",
+      "--revision_mapping_file",
+      "{}",
       "--output_json",
       "/path/to/tmp/json"
     ],
@@ -123,6 +125,8 @@
       "totallyanandroid-m1",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_deps': {'src/blacklist/project/1': None, 'src/blacklist/project/2': None}, 'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'svn://svn-mirror.golo.chromium.org/blink/trunk'}, 'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}]\ntarget_os = ['android']",
+      "--revision_mapping_file",
+      "{}",
       "--output_json",
       "/path/to/tmp/json"
     ],