Bump linux_chromium_ozone_compile_only_ng to 50%.

This bumps the experimental builder to 50% and also
marks it as "compile_only", which means that we don't
include any debug symbols (this speeds up the build).

R=jbudorick@chromium.org
BUG=694033

Change-Id: I73713462395bcc360172883aa898af72c8a8ecd7
Reviewed-on: https://chromium-review.googlesource.com/898366Reviewed-by: John Budorick <jbudorick@google.com>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534832}

infra/config/cq.cfg

@@ -94,7 +94,7 @@ verifiers {
       }
       builders {
         name: "linux_chromium_ozone_compile_only_ng"
-        experiment_percentage: 10
+        experiment_percentage: 50
       }
       builders {
         name: "linux_chromium_compile_dbg_ng"

tools/mb/mb_config.pyl

@@ -631,8 +631,7 @@
       'linux_chromium_dbg_ng': 'debug_trybot',
       'linux_chromium_gn_upload': 'gn_linux_upload',
       'linux_chromium_headless_rel': 'headless_linux_release_trybot',
-      'linux_chromium_ozone_compile_only_ng': 'ozone_linux_release_trybot',
-      'linux_chromium_ozone_ng': 'ozone_linux_release_trybot',
+      'linux_chromium_ozone_compile_only_ng': 'ozone_linux_release_trybot_compile_only',
 
       # This is intentionally a release_bot and not a release_trybot;
       # enabling DCHECKs seems to cause flaky failures that don't show up
@@ -1487,8 +1486,8 @@
       'ozone_linux', 'release_bot',
     ],
 
-    'ozone_linux_release_trybot': [
-      'ozone_linux', 'release_trybot',
+    'ozone_linux_release_trybot_compile_only': [
+      'ozone_linux', 'release_trybot', 'compile_only',
     ],
 
     'presubmit': [