Add components_browsertests to trybot.

This CL adds the components_browsertests target to android, linux,
mac and windows platforms.

BUG=311270

Review URL: https://codereview.chromium.org/578653003

Cr-Commit-Position: refs/heads/master@{#295199}

testing/buildbot/chromium_trybot.json

@@ -30,6 +30,7 @@
       "test": "chrome_elf_unittests",
       "platforms": ["win"]
     },
+    "components_browsertests",
     "components_unittests",
     {
       "test": "compositor_unittests",