Add Win7 (32) Tests builder to buildbucket

Bug: 790648
Change-Id: I3b937866dec75cd62485f44cdd74a54dc78634f6
Reviewed-on: https://chromium-review.googlesource.com/944563Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540362}

infra/config/global/cr-buildbucket.cfg

@@ -327,15 +327,24 @@ buckets {
       dimensions: "cpu:x86-64"
       dimensions: "cores:32"
     }
+    builders {
+      name: "Win7 (32) Tests"
+      mixins: "win-ci"
+      dimensions: "os:Windows-7"
+      dimensions: "cpu:x86-64"
+      dimensions: "cores:8"
+    }
     builders {
       name: "Win7 Tests (1)"
       mixins: "win-ci"
+      dimensions: "os:Windows-7"
       dimensions: "cpu:x86-64"
       dimensions: "cores:8"
     }
     builders {
       name: "Win7 Tests (dbg)(1)"
       mixins: "win-ci"
+      dimensions: "os:Windows-7"
       dimensions: "cpu:x86-64"
       dimensions: "cores:8"
     }