Add gpu_manual_try_win7_nvidia_rel trybot config.

Add a manually triggered GPU trybot that runs the same configuration
as "Win7 FYI Release (NVIDIA)".

Bug: 838895
Change-Id: I2a2f87ee7b452200a860282b01c673493adbea00
Reviewed-on: https://chromium-review.googlesource.com/1044767Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556175}

infra/config/global/cr-buildbucket.cfg

@@ -1443,6 +1443,7 @@ buckets {
     builders { mixins: "mac-try" name: "mac_upload_clang" }
     builders { mixins: "mac-try" name: "mac-views-rel" }
 
+    builders { mixins: "win-optional-gpu-try" name: "gpu_manual_try_win7_nvidia_rel" }
     builders { mixins: "win-try" name: "win10_chromium_x64_dbg_ng" }
     builders { mixins: "win-try" name: "win10_chromium_x64_rel_ng" }
     builders { mixins: "win-try" name: "win10_chromium_x64_rel_ng_exp" }

infra/config/global/luci-milo.cfg

@@ -4207,6 +4207,9 @@ consoles: {
   header_id: "chromium"
   builder_view_only: true
 
+  builders: {
+    name: "buildbucket/luci.chromium.try/gpu_manual_try_win7_nvidia_rel"
+  }
   builders: {
     name: "buildbucket/luci.chromium.try/win10_chromium_x64_dbg_ng"
   }
@@ -4473,6 +4476,9 @@ consoles: {
   builders: {
     name: "buildbucket/luci.chromium.try/fuchsia"
   }
+  builders: {
+    name: "buildbucket/luci.chromium.try/gpu_manual_try_win7_nvidia_rel"
+  }
   builders: {
     name: "buildbucket/luci.chromium.try/linux-blink-heap-incremental-marking"
   }

tools/mb/mb_config.pyl

@@ -684,6 +684,7 @@
     },
 
     'tryserver.chromium.win': {
+      'gpu_manual_try_win7_nvidia_rel': 'gpu_fyi_tests_release_trybot_x86',
       'win7_chromium_rel_ng': 'gpu_tests_release_trybot_x86_minimal_symbols',
       'win7_chromium_rel_loc_exp': 'gpu_tests_release_trybot_x86_minimal_symbols',
       'win10_chromium_x64_rel_ng': 'release_trybot',