Revert "infra: Add and use mixins for Goma RBE server settings"

This reverts commit 58e8d8c6.

Reason for revert: Cannot combine mixins

Original change's description:
> infra: Add and use mixins for Goma RBE server settings
> 
> R=​tikuta@chromium.org, ukai@chromium.org, yyanagisawa@chromium.org
> 
> Bug: 945701
> Change-Id: I98b2a8a2d644eccde84224171bbe7e9885041046
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539416
> Commit-Queue: Simon Que <sque@chromium.org>
> Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#644219}

TBR=sque@chromium.org,ukai@chromium.org,yyanagisawa@chromium.org,tikuta@chromium.org

Change-Id: Ife0174d62bec2bf99d75647b864fd6c7992fa30e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 945701
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539490Reviewed-by: Simon Que <sque@chromium.org>
Commit-Queue: Simon Que <sque@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644690}

infra/config/cr-buildbucket.cfg

@@ -135,46 +135,6 @@ builder_mixins {
   }
 }
 
-# Enables use of Goma RBE ToT backend in a builder.
-builder_mixins {
-  name: "goma-rbe-tot"
-  recipe {
-    properties_j: <<END
-    $build/goma: {
-      "server_host": "rbe-tot.endpoints.cxx-compiler-service.cloud.goog"
-    }
-    END
-  }
-}
-
-# Enables use of Goma RBE Mixer Staging backend in a builder.
-builder_mixins {
-  name: "goma-rbe-mixer-staging"
-  recipe {
-    properties_j: <<END
-    $build/goma: {
-      "server_host": "staging-goma.chromium.org",
-      "rpc_extra_params": "?staging"
-    }
-    END
-  }
-}
-
-# TODO(ukai): add goma-rbe-mixer-prod
-
-# Enables use of Goma RBE Prod backend in a builder.
-builder_mixins {
-  name: "goma-rbe-prod"
-  recipe {
-    properties_j: <<END
-    $build/goma: {
-      "server_host": "goma.chromium.org",
-      "rpc_extra_params": "?prod"
-    }
-    END
-  }
-}
-
 builder_mixins {
   name: "android"
   dimensions: "os:Android"
@@ -2567,7 +2527,6 @@ buckets {
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Linux Goma RBE ToT (ATS)"
@@ -2575,63 +2534,54 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ats"
       mixins: "goma-ci"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Linux Goma RBE Staging"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Linux Goma RBE Staging (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Linux Goma RBE Staging (dbg)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Linux Goma RBE Staging (dbg) (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Linux Goma RBE Prod"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Linux Goma RBE Prod (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Linux Goma RBE Prod (dbg)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Linux Goma RBE Prod (dbg) (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Linux Goma RBE LoadTest"
@@ -2696,7 +2646,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ci"
       mixins: "goma-j80"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Mac Goma RBE Staging (clobber)"
@@ -2705,7 +2654,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ci"
       mixins: "goma-j80"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Mac Goma RBE Staging"
@@ -2714,7 +2662,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ci"
       mixins: "goma-j80"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Mac Goma RBE Staging (dbg)"
@@ -2723,7 +2670,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ci"
       mixins: "goma-j80"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Win Goma RBE ToT"
@@ -2731,7 +2677,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ats"
       mixins: "goma-ci"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Win Goma RBE Staging"
@@ -2739,7 +2684,6 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ats"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Win Goma RBE Staging (clobber)"
@@ -2747,14 +2691,12 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ats"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE ToT"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE ToT (ATS)"
@@ -2762,42 +2704,36 @@ buckets {
       mixins: "experimental"
       mixins: "goma-ats"
       mixins: "goma-ci"
-      mixins: "goma-rbe-tot"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Staging"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-mixer-staging"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Prod"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Prod (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Prod (dbg)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Prod (dbg) (clobber)"
       dimensions: "os:Ubuntu-14.04"
       mixins: "experimental"
       mixins: "goma-ci"
-      mixins: "goma-rbe-prod"
     }
     builders {
       name: "Chromium Mac Goma Staging"