Add builder for horizontal class merging

Change-Id: I78f72d81d8a927ccdf2d3fc5c9752ea000f4590d
diff --git a/infra/config/global/cr-buildbucket.cfg b/infra/config/global/cr-buildbucket.cfg
index 4fc504a..2b6eb5f 100644
--- a/infra/config/global/cr-buildbucket.cfg
+++ b/infra/config/global/cr-buildbucket.cfg
@@ -149,6 +149,15 @@
       }
     }
     builders {
+      name: "linux_horizontal"
+      mixins: "linux"
+      mixins: "normal"
+      recipe {
+        properties: "tool:r8"
+        properties: "horizontal_class_merging:True"
+      }
+    }
+    builders {
       name: "linux_release"
       mixins: "normal"
       mixins: "linux"
diff --git a/infra/config/global/luci-milo.cfg b/infra/config/global/luci-milo.cfg
index faf51f3..90e3efc 100644
--- a/infra/config/global/luci-milo.cfg
+++ b/infra/config/global/luci-milo.cfg
@@ -16,6 +16,11 @@
     short_name: "linux"
   }
   builders {
+    name: "buildbucket/luci.r8.ci/linux_horizontal"
+    category: "R8"
+    short_name: "horizontal"
+  }
+  builders {
     name: "buildbucket/luci.r8.ci/linux-android-4.0.4"
     category: "R8"
     short_name: "4.0.4"
diff --git a/infra/config/global/luci-notify.cfg b/infra/config/global/luci-notify.cfg
index 5e37d53..e417700 100644
--- a/infra/config/global/luci-notify.cfg
+++ b/infra/config/global/luci-notify.cfg
@@ -29,6 +29,11 @@
     repository: "https://r8.googlesource.com/r8"
   }
   builders {
+    name: "linux_horizontal"
+    bucket: "ci"
+    repository: "https://r8.googlesource.com/r8"
+  }
+  builders {
     name: "linux_release"
     bucket: "ci"
     repository: "https://r8.googlesource.com/r8"
diff --git a/infra/config/global/luci-scheduler.cfg b/infra/config/global/luci-scheduler.cfg
index eb725d9..3c31451 100644
--- a/infra/config/global/luci-scheduler.cfg
+++ b/infra/config/global/luci-scheduler.cfg
@@ -27,6 +27,7 @@
   }
   triggers: "archive"
   triggers: "linux"
+  triggers: "linux_horizontal"
   triggers: "linux-android-4.0.4"
   triggers: "linux-android-4.4.4"
   triggers: "linux-android-5.1.1"
@@ -136,6 +137,19 @@
 }
 
 job {
+  id: "linux_horizontal"
+  acl_sets: "default"
+  triggering_policy: {
+    max_concurrent_invocations: 3
+  }
+  buildbucket {
+    server: "cr-buildbucket.appspot.com"
+    bucket: "luci.r8.ci"
+    builder: "linux_horizontal"
+  }
+}
+
+job {
   id: "linux-android-4.0.4"
   acl_sets: "default"
   triggering_policy: {