Add a recipe to identify culprits for chromium compile failures.

scripts/slave/recipe_modules/filter/api.py

Index: scripts/slave/recipe_modules/filter/api.py
diff --git a/scripts/slave/recipe_modules/filter/api.py b/scripts/slave/recipe_modules/filter/api.py
index 359c2a41fd41ff613af68a88497effc3d021f945..e795b96a9eed5f1a9e3ecb4b0e252d4f89572f61 100644
--- a/scripts/slave/recipe_modules/filter/api.py
+++ b/scripts/slave/recipe_modules/filter/api.py
@@ -160,14 +160,25 @@ class FilterApi(recipe_api.RecipeApi):
         # Ensure that mb runs in a clean environment to avoid
         # picking up any GYP_DEFINES accidentally.
         del kwargs['env']
+      # We need to use the actual mastername and buildername we're running on,

[Paweł Hajdan Jr., 2015/11/24 13:20:41]

Could you extract this to a separate CL? Such changes are quite risky to land,
so I'd like to minimize that risk and simplify analyzing the blamelist.

[stgao, 2015/11/24 23:19:19]

Done.

https://codereview.chromium.org/1474473004/

+      # because it may be configured with different MB settings from those for
+      # the continuous builder a trybot may be configured to match.
+      # However, use target_mastername and target_buildername instead if they
+      # are available in the build properties. This gives a recipe running on a
+      # trybot the flexibility to run MB in exactly the same configuration as
+      # the continuous builder it tries to match.
+      target_mastername = (self.m.properties.get('target_mastername') or
+                           self.m.properties['mastername'])
+      target_buildername = (self.m.properties.get('target_buildername') or
+                            self.m.properties['buildername'])
       step_result = self.m.python(
           'analyze',
           self.m.path['checkout'].join('tools', 'mb', 'mb.py'),
           args=['analyze',
                 '-m',
-                self.m.properties['mastername'],
+                target_mastername,
                 '-b',
-                self.m.properties['buildername'],
+                target_buildername,
                 '-v',
                 build_output_dir,
                 self.m.json.input(analyze_input),