Add Android to SkiaRenderer field trial

Bug: 1019787
Change-Id: I3f3121b7da6e46a9558ac0a2058b9ba8239fea84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2078772
Auto-Submit: Jonathan Backer <backer@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746352}

testing/variations/fieldtrial_testing_config.json

@@ -5884,6 +5884,7 @@
     "UseSkiaRenderer": [
         {
             "platforms": [
+                "android",
                 "linux",
                 "windows"
             ],