[test] Add arm perf trybot to runner script.

BUG=chromium:484589
LOG=n
NOTRY=true
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1123473007

Cr-Commit-Position: refs/heads/master@{#28227}

tools/try_perf.py

@@ -12,6 +12,7 @@ find_depot_tools.add_depot_tools_to_path()
 from git_cl import Changelist
 
 BOTS = {
+  '--arm32': 'v8_arm32_perf_try',
   '--linux32': 'v8_linux32_perf_try',
   '--linux64': 'v8_linux64_perf_try',
   '--linux64_haswell': 'v8_linux64_haswell_perf_try',