Treat bisect/tryjob perf test failures as warnings.

scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json

Index: scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json
diff --git a/scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json b/scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json
index 2cc0442a58d325a6f93e64fd72f62d7830d12e0d..f7ffcabc6141a0caa2853cadfe994db88bf42675 100644
--- a/scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json
+++ b/scripts/slave/recipe_modules/auto_bisect_staging/example.expected/return_code.json
@@ -1023,7 +1023,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1077,7 +1077,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1131,7 +1131,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1185,7 +1185,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1239,7 +1239,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1525,7 +1525,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1579,7 +1579,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1633,7 +1633,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1687,7 +1687,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {
@@ -1741,7 +1741,7 @@
       "step returned non-zero exit code: 1",
       "@@@STEP_LOG_LINE@Failure Output@benchmark text@@@",
       "@@@STEP_LOG_END@Failure Output@@@",
-      "@@@STEP_FAILURE@@@"
+      "@@@STEP_WARNINGS@@@"
     ]
   },
   {