(reland) Check missing headers in the build on CQ

testing/buildbot/chromium.linux.json

 {
   "Android Arm64 Builder (dbg)": {
     "additional_compile_targets": [
       "all"
     ]
   },
   "Android Builder": {
     "additional_compile_targets": [
       "cronet_test_instrumentation_apk",
       "system_webview_apk"
@@ skipping 3501 matching lines @@
         "swarming": {
           "can_use_on_swarming_builders": false
         },
         "test": "url_unittests"
       }
     ]
   },
   "Linux Builder": {
     "additional_compile_targets": [
       "all"
+    ],
+    "scripts": [

[Dirk Pranke, 2017/05/25 01:39:31]

Why are you moving these from the "Linux Tests" builder? Is it because the Tests
builder doesn't have a full checkout?

I'm not sure that and test entries on a build-only bot will even be run, so that
might be something we need to change ...

[wychen, 2017/05/25 02:05:24]

Exactly. The analysis relies on having a fully compiled OUT_DIR.
It runs fine. See the trybot results in PS2 and PS3.

+      {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      }
     ]
   },
   "Linux Builder (dbg)": {
     "additional_compile_targets": [
       "all"
+    ],
+    "scripts": [
+      {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      }
     ]
   },
   "Linux Tests": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "accessibility_unittests"
       },
@@ skipping 1642 matching lines @@
         "isolate_name": "telemetry_unittests",
         "name": "telemetry_unittests",
         "swarming": {
           "can_use_on_swarming_builders": true,
           "shards": 4
         }
       }
     ]
   }
 }