Collect failed "target"s from ninja in the compile step on Waterfall.

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 9074871496a1250a7efa6b6d235805ca8fcc9566..cd21580bb227c77ae7f5bc914677876043bae253 100644
--- a/scripts/slave/recipe_modules/chromium/api.py
+++ b/scripts/slave/recipe_modules/chromium/api.py
@@ -166,6 +166,11 @@ class ChromiumApi(recipe_api.RecipeApi):
       args += ['--build-args', self.c.compile_py.build_args]
     if self.c.compile_py.build_tool:
       args += ['--build-tool', self.c.compile_py.build_tool]
+      if self.c.compile_py.build_tool == 'ninja':
+        # Collect info of compile failure from ninja 1.7+.
+        args += [
+          '--ninja-compile-failure',
+          self.m.json.output(add_json_log=False, name='ninja-compile-failure')]
     if self.m.properties.get('build_data_dir'):
       args += ['--build-data-dir', self.m.properties.get('build_data_dir')]
     if self.c.compile_py.cross_tool:
@@ -254,6 +259,17 @@ class ChromiumApi(recipe_api.RecipeApi):
           properties['extra_result_code'].append(failure_result_code)
           raise self.m.step.InfraFailure('Infra compile failure: %s' % e)
 
+      if self.c.compile_py.build_tool == 'ninja':
+        # Report failed compile "target"s from ninja as a build property so that
+        # automated tools/service like Findit could use them for the purpose of
+        # culprit finding, etc.
+        # When there is an infra failure like goma outage above, no info is
+        # collected from ninja.
+        step_result = self.m.step.active_result
+        failures = (step_result.json.outputs['ninja-compile-failure'] or
+                    {'unknown_failures': True})
+        step_result.presentation.properties['compile_failures'] = failures
+
       raise e
 
   @recipe_util.returns_placeholder