Add Mac10.12 continuous builder and try bot config (src repo).

testing/buildbot/chromium.webkit.json

Index: testing/buildbot/chromium.webkit.json
diff --git a/testing/buildbot/chromium.webkit.json b/testing/buildbot/chromium.webkit.json
index 303e77194f10e7fe039cfe10fdf0d033fcfb51cf..d181eaa2d4376299a45536045010bf70a99302ea 100644
--- a/testing/buildbot/chromium.webkit.json
+++ b/testing/buildbot/chromium.webkit.json
@@ -217,6 +217,44 @@
       }
     ]
   },
+  "WebKit Mac10.12": {
+    "gtest_tests": [
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "blink_heap_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "blink_platform_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "webkit_unit_tests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "wtf_unittests"
+      }
+    ],
+    "scripts": [
+      {
+        "name": "webkit_lint",
+        "script": "webkit_lint.py"
+      },
+      {
+        "name": "webkit_python_tests",
+        "script": "webkit_python_tests.py"
+      }
+    ]
+  },
   "WebKit Mac10.9": {
     "gtest_tests": [
       {