Use GN in simple chrome builders

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index 2970b45c77441f15178b4987471d56674a1db572..dc9b573728075fbf452748f30869143e3fda7c13 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -66,9 +66,9 @@
     },
 
     'chromium.chromiumos': {
-      'ChromiumOS amd64-generic Compile': 'cros_chrome_sdk_gyp',
-      'ChromiumOS daisy Compile': 'cros_chrome_sdk_gyp',
-      'ChromiumOS x86-generic Compile': 'cros_chrome_sdk_gyp',
+      'ChromiumOS amd64-generic Compile': 'cros_chrome_sdk_gn',
+      'ChromiumOS daisy Compile': 'cros_chrome_sdk_gn',
+      'ChromiumOS x86-generic Compile': 'cros_chrome_sdk_gn',
       'Linux ChromiumOS Builder': 'swarming_chromeos_gyp_release_bot',
       'Linux ChromiumOS Builder (dbg)': 'swarming_chromeos_gyp_debug_bot',
       'Linux ChromiumOS Full': 'swarming_chromeos_gyp_release_bot',
@@ -1051,6 +1051,9 @@
     'cros_chrome_sdk_gyp': [
       'gyp', 'cros_chrome_sdk',
     ],
+    'cros_chrome_sdk_gn': [
+      'gn', 'cros_chrome_sdk',
+    ],
 
     # The 'findit' config is used by the *_variable_* bots, which run
     # the 'FindIt' recipes and code to bisect failures that happen on the