Attempt to make GN waterfall bots not on the CQ alert but not close trees.

scripts/slave/gatekeeper.json

 {
   "comment": ["This is a configuration file for gatekeeper_ng.py",
               "Look at that for documentation on this file's format."],
 
   "masters": {
     "https://build.chromium.org/p/chromium": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
@@ skipping 240 matching lines @@
         "builders": {
           "*": {}
         }
       }
     ],
     "https://build.chromium.org/p/chromium.mac": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
+        "comment": [
+          "TODO(dpranke): crbug.com/486089, crbug.com/439402",
+          "Until the Mac GN (dbg) bot is in the CQ, it should not close the",
+          "tree."
+        ],
         "builders": {
           "iOS_Device": {
             "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"]
           },
           "iOS_Simulator_(dbg)": {
             "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"],
             "closing_optional": [],
             "comment": ["closing_optional due to crbug.com/393861"]
           },
           "iOS_Device_(ninja)": {
             "sheriff_classes": ["sheriff_ios_europe", "sheriff_ios_us"]
           },
+          "Mac GN (dbg)": {
+            "close_tree": false

[ghost stip (do not use), 2016/02/26 01:01:51]

IIUC this feature isn't particularly used and may have suffered bitrot.
regardless, the codepaths seem to respect it

+          },
           "*": {}
-        },
-
-        "comment": [
-          "TODO(dpranke): crbug.com/486089, crbug.com/439402",
-          "Until these are in the CQ, they should not close the tree."
-        ],
-        "excluded_builders": [
-          "Mac GN (dbg)"
-        ]
-
+        }
       }
     ],
     "https://build.chromium.org/p/chromium.memory": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
         "builders": {
           "*": {}
         }
@@ skipping 91 matching lines @@
             ]
           }
         }
       }
     ],
     "https://build.chromium.org/p/chromium.win": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
-        "builders": {
-          "*": {}
-        },
 
         "comment": [
           "TODO(dpranke): crbug.com/486089, crbug.com/439402",
-          "Until these are in the CQ, they should not close the tree."
+          "Until the GN bots are in the CQ, they should not close the tree."
         ],
-        "excluded_builders": [
-          "Win x64 GN",
-          "Win x64 GN (dbg)",
-          "Win8 GN (dbg)"
-        ]
+        "builders": {
+          "Win x64 GN": {
+            "close_tree": false
+          },
+          "Win x64 GN (dbg)": {
+            "close_tree": false
+          },
+          "Win8 GN (dbg)": {
+            "close_tree": false
+          },
+          "*": {}
+        }
       }
     ],
     "https://build.chromium.org/p/client.boringssl": [
       {
         "tree_notify": [
           "davidben+boringssl@google.com",
           "agl+boringssl@google.com"
         ],
 
         "forgive_all": "true",
@@ skipping 464 matching lines @@
         "cleanup_temp",
         "taskkill"
       ],
       "closing_optional": [
         "compile",
         "gn"
       ]
     }
   }
 }