Add some comments for preparing WebKit Win10 migration.

BUG=790343

Change-Id: Ifb62914414b09eed794387ab5073fc973532f162
Reviewed-on: https://chromium-review.googlesource.com/1249807Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Jao-ke Chin-Lee <jchinlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594843}

infra/config/global/cr-buildbucket.cfg

@@ -2106,6 +2106,7 @@ buckets {
     }
     builders {
       name: "WebKit Win Builder"
+      # This may be obsolete (WebKit Win10 is triggered by Win Builder).
       dimensions: "os:Windows-10"
       mixins: "webkit-ci"
     }

infra/config/global/luci-milo.cfg

@@ -701,6 +701,7 @@ consoles {
   }
   builders {
     name: "buildbot/chromium.webkit/WebKit Win10"
+    name: "buildbucket/luci.chromium.ci/WebKit Win10"
     category: "chromium.webkit|win rel|tester"
     short_name: "10"
   }

infra/config/global/luci-scheduler.cfg

@@ -3621,6 +3621,7 @@ job {
 
 job {
   id: "WebKit Win Builder"
+  # This may be obsolete (WebKit Win10 is triggered by Win Builder).
   acl_sets: "default"
   buildbucket: {
     server: "cr-buildbucket.appspot.com"
@@ -3631,7 +3632,7 @@ job {
 
 job {
   id: "WebKit Win10"
-  # Triggered by "WebKit Win Builder"
+  # Triggered by "Win Builder"
   acl_sets: "triggered-by-parent-builders"
   buildbucket: {
     server: "cr-buildbucket.appspot.com"