Revert "trusty -> xenial for linux try/ci builders"

This reverts commit 2aef1e3c.

Reason for revert: crbug.com/971133

Original change's description:
> trusty -> xenial for linux try/ci builders
> 
> This will be submitted after
> https://chrome-internal-review.googlesource.com/c/infradata/config/+/1358390
> 
> But test for linux-ozone-rel is still configured to use trusty due to
> https://ci.chromium.org/p/chromium/builders/try/linux-ozone-rel/283303
> 
> Bug: 954450
> Change-Id: Ie2d93ccc409dbc494b15fdb4039aa1e7a44660c5
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1642851
> Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
> Reviewed-by: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#666172}

TBR=yyanagisawa@chromium.org,tikuta@chromium.org,bpastene@chromium.org,jbudorick@chromium.org

Change-Id: Ia1e79e2b720b928c6d84cde954b5eb112113e3c1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 954450, 971133
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1645136Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666188}

infra/config/cr-buildbucket.cfg

@@ -1417,7 +1417,6 @@ buckets {
     builders {
       name: "Leak Detection Linux"
       mixins: "linux-ci-goma-rbe-prod"
-      mixins: "linux-xenial"
     }
 
     builders {
@@ -1438,7 +1437,6 @@ buckets {
       name: "Linux ASan Tests (sandboxed)"
       mixins: "linux"
       mixins: "memory-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
@@ -1458,7 +1456,6 @@ buckets {
       name: "linux-blink-animation-use-time-delta"
       dimensions: "os:Ubuntu-14.04"
       mixins: "fyi-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
@@ -1472,20 +1469,17 @@ buckets {
       name: "linux-blink-heap-verification"
       mixins: "fyi-ci"
       mixins: "linux"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux-blink-heap-unified-gc"
       mixins: "fyi-ci"
       mixins: "linux"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux_chromium_component_updater"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
       recipe {
         name: "findit/chromium/update_components"
       }
@@ -1496,32 +1490,27 @@ buckets {
       name: "linux-chromium-tests-staging-builder"
       mixins: "fyi-ci"
       mixins: "linux"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux-chromium-tests-staging-tests"
       mixins: "fyi-ci"
       mixins: "linux"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux-gcc-rel"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux-jumbo-rel"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "linux-ozone-rel"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
@@ -1539,13 +1528,11 @@ buckets {
     builders {
       name: "Linux Tests (dbg)(1)"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
       name: "Linux Tests (dbg)(1)(32)"
       mixins: "linux-ci"
-      mixins: "linux-xenial"
     }
 
     builders {
@@ -3667,7 +3654,6 @@ buckets {
     }
     builders {
       mixins: "linux-try"
-      mixins: "linux-xenial"
       name: "closure_compilation"
       recipe {
         name: "closure_compilation"
@@ -3723,7 +3709,6 @@ buckets {
     builders {
       mixins: "linux-try"
       mixins: "goma-rbe-prod"
-      mixins: "linux-xenial"
       name: "leak_detection_linux"
     }
     builders { mixins: "linux-angle-try" name: "fuchsia-angle-rel" }
@@ -3744,36 +3729,18 @@ buckets {
       mixins: "linux-try"
       name: "linux-blink-heap-concurrent-marking-tsan-rel"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux-blink-heap-verification-try"
-    }
-    builders {
-       mixins: "linux-try"
-       mixins: "linux-xenial"
-       name: "linux-dcheck-off-rel"
-    }
+    builders { mixins: "linux-try" name: "linux-blink-heap-verification-try" }
+    builders { mixins: "linux-try" name: "linux-dcheck-off-rel" }
     builders {
       mixins: "linux-try"
       mixins: "goma-j150"
-      mixins: "linux-xenial"
       name: "linux-goma-rbe-staging-rel"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux-gcc-rel"
-    }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux-jumbo-rel"
-    }
+    builders { mixins: "linux-try" name: "linux-gcc-rel" }
+    builders { mixins: "linux-try" name: "linux-jumbo-rel" }
     builders {
       name: "linux-libfuzzer-asan-rel"
       mixins: "linux-try"
-      mixins: "linux-xenial"
       recipe {
         name: "chromium_libfuzzer_trybot"
       }
@@ -3791,19 +3758,10 @@ buckets {
     builders {
       mixins: "linux-try"
       mixins: "goma-rbe-prod-ats"
-      mixins: "linux-xenial"
       name: "linux_arm"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_analysis"
-    }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_archive_rel_ng"
-    }
+    builders { mixins: "linux-try" name: "linux_chromium_analysis" }
+    builders { mixins: "linux-try" name: "linux_chromium_archive_rel_ng" }
     builders {
       mixins: "linux-try"
       mixins: "linux-xenial"
@@ -3830,30 +3788,16 @@ buckets {
       name: "linux_chromium_clobber_deterministic",
       mixins: "linux-try"
       mixins: "deterministic"
-      mixins: "linux-xenial"
-    }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_clobber_rel_ng"
-    }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_compile_dbg_32_ng"
     }
+    builders { mixins: "linux-try" name: "linux_chromium_clobber_rel_ng" }
+    builders { mixins: "linux-try" name: "linux_chromium_compile_dbg_32_ng" }
     builders {
       mixins: "linux-try"
       mixins: "linux-debug-cache"
       mixins: "goma-j150"
-      mixins: "linux-xenial"
       name: "linux_chromium_compile_dbg_ng"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_compile_rel_ng"
-    }
+    builders { mixins: "linux-try" name: "linux_chromium_compile_rel_ng" }
     builders {
       mixins: "linux-try"
       mixins: "goma-rbe-prod"
@@ -3863,19 +3807,16 @@ buckets {
       mixins: "linux-try"
       mixins: "linux-debug-cache"
       mixins: "goma-rbe-prod"
-      mixins: "linux-xenial"
       name: "linux_chromium_dbg_ng"
     }
     builders {
       mixins: "linux-try"
       mixins: "goma-rbe-prod-j150"
-      mixins: "linux-xenial"
       name: "linux_chromium_msan_rel_ng"
     }
     builders {
       mixins: "linux-try"
       mixins: "goma-j150"
-      mixins: "linux-xenial"
       name: "linux-coverage-rel"
     }
     builders {
@@ -3890,30 +3831,17 @@ buckets {
       mixins: "goma-j150"
       name: "linux_chromium_tsan_rel_ng"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_chromium_ubsan_rel_ng"
-    }
+    builders { mixins: "linux-try" name: "linux_chromium_ubsan_rel_ng" }
     builders {
       mixins: "linux-dawn-try"
       mixins: "goma-rbe-prod"
       name: "linux-dawn-rel"
     }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_layout_tests_composite_after_paint"
-    }
-    builders {
-      mixins: "linux-try"
-      mixins: "linux-xenial"
-      name: "linux_layout_tests_layout_ng"
-    }
+    builders { mixins: "linux-try" name: "linux_layout_tests_composite_after_paint" }
+    builders { mixins: "linux-try" name: "linux_layout_tests_layout_ng" }
     builders {
       mixins: "linux-try"
       mixins: "goma-rbe-prod"
-      mixins: "linux-xenial"
       name: "linux_mojo"
     }
     builders { mixins: "linux-try" name: "linux_mojo_chromeos" }
@@ -4196,14 +4124,12 @@ buckets {
       name: "linux-annotator-rel"
       dimensions: "os:Ubuntu-14.04"
       mixins: "linux-try"
-      mixins: "linux-xenial"
     }
     builders {
       name: "linux_vr"
       dimensions: "os:Ubuntu-14.04"
       mixins: "linux-try"
       mixins: "goma-rbe-prod"
-      mixins: "linux-xenial"
     }
     builders {
       name: "android_compile_rel"
@@ -4231,7 +4157,6 @@ buckets {
       dimensions: "os:Ubuntu-14.04"
       mixins: "linux-try"
       mixins: "goma-rbe-prod"
-      mixins: "linux-xenial"
     }
     builders {
       name: "android_cfi_rel_ng"