Run gyp_flag_compare.py on Linux GN bots

scripts/slave/recipe_modules/chromium/api.py

Index: scripts/slave/recipe_modules/chromium/api.py
diff --git a/scripts/slave/recipe_modules/chromium/api.py b/scripts/slave/recipe_modules/chromium/api.py
index 9173de384d56a02179657b042b07d0c8c4df90b8..f6242b7129ca12ff9c4d58ff5c896e120724050c 100644
--- a/scripts/slave/recipe_modules/chromium/api.py
+++ b/scripts/slave/recipe_modules/chromium/api.py
@@ -430,6 +430,16 @@ class ChromiumApi(recipe_api.RecipeApi):
             '--args=%s' % ' '.join(gn_args),
         ])
 
+  def run_gn_compare(self):
+    """Run the gyp/GN flag comparison tool to generate a report on flag
+    differences between the builds."""
+    self.m.python(
+        name='gyp_flag_compare',
+        script=self.m.path['checkout'].join('tools/gn/bin/gyp_flag_compare.py'),
+        args=[
+            'chrome',  # TODO(scottmg): all, configurable, etc.
+        ])
+
   def taskkill(self):
     self.m.python(
       'taskkill',