Add a presubmit builder.

This runs the run_presubmit canned recipe. It should work the same as
it would in Chromium or Dawn or most other repos. It should prevent
rollers and devs from landing several common types of dirty changes.

This CL adds the builder that then we can test manually before adding
it to the CQ.

Bug: angleproject:3288
Change-Id: I45e78669d0b6c34cef50ab9cb45c33a1b8bb6aca
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1548293
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

infra/config/global/cr-buildbucket.cfg

@@ -117,6 +117,16 @@ buckets {
       }
     }
 
+    builders {
+      name: "presubmit"
+      dimensions: "os:Ubuntu-14.04"
+      recipe {
+        name: "run_presubmit"
+        properties: "repo_name:angle"
+        properties_j: "runhooks:true"
+      }
+    }
+
     builders {
       name: "linux-clang-dbg"
       mixins: "linux"

infra/config/global/luci-milo.cfg

@@ -89,6 +89,9 @@ consoles {
   refs: "refs/heads/master"
   manifest_name: "PATCHED"
 
+  builders {
+    name: "buildbucket/luci.angle.try/presubmit"
+  }
   builders {
     name: "buildbucket/luci.angle.try/linux-clang-dbg"
     category: "linux|clang"