Add check_gn_headers.py to find missing headers in GN

testing/buildbot/chromium.linux.json

Index: testing/buildbot/chromium.linux.json
diff --git a/testing/buildbot/chromium.linux.json b/testing/buildbot/chromium.linux.json
index 5dd210d2de1cab38a9c26d1ec8ff96b4a47e63c4..b77e143e2f9c3b8e65e0ef4834b72673ae89bf4b 100644
--- a/testing/buildbot/chromium.linux.json
+++ b/testing/buildbot/chromium.linux.json
@@ -1293,6 +1293,12 @@
       {
         "test": "webapk_shell_apk_junit_tests"
       }
+    ],
+    "scripts": [
+      {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      }

[Dirk Pranke, 2017/01/09 06:47:49]

As I noted in the bug, it's not immediately clear how to make this work as a
test step on the bots. Let's leave this file unmodified and leave the
//testing/scripts/check_gn_headers.py file out of this CL, so that we can land
the rest.

[wychen, 2017/01/09 13:14:53]

I've removed them from this CL.

According to my design doc, the stale .d file can be eliminated if this checking
is only done after a full compile. As for the skipped analysis, even though
temporary regression could happen, new errors would eventually be discovered.

Quote: "Note that it can go wrong only if a new header is exclusively included
by whitelisted headers. If the new header is also included by any cc files, “gn
analyze” would trigger compilation. Therefore, the error scenario should be
infrequent enough so that sheriffs could revert the culprit without too much
difficulty."

Do you think it's better to wait until we have PRESUBMIT heuristics to
complement the checking on CQ?

     ]
   },
   "Android Tests (dbg)": {
@@ -2568,6 +2574,12 @@
       {
         "test": "webapk_shell_apk_junit_tests"
       }
+    ],
+    "scripts": [
+      {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      }
     ]
   },
   "Blimp Linux (dbg)": {
@@ -3422,6 +3434,10 @@
     ],
     "scripts": [
       {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      },
+      {
         "name": "checkdeps",
         "script": "checkdeps.py"
       },
@@ -3984,6 +4000,10 @@
     ],
     "scripts": [
       {
+        "name": "check_gn_headers",
+        "script": "check_gn_headers.py"
+      },
+      {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }