Add components_browsertests to trybot.

testing/buildbot/chromium_trybot.json

 {
   "compile_targets": [
     "all"
   ],
   "gtest_tests": [
     "accessibility_unittests",
     "app_list_unittests",
     {
       "test": "base_unittests",
       "swarming": {
@@ skipping 12 matching lines @@
     "cc_unittests",
     "chromedriver_unittests",
     {
       "test": "chromevox_tests",
       "chromium_configs": ["chromium_chromeos", "chromium_chromeos_clang"]
     },
     {
       "test": "chrome_elf_unittests",
       "platforms": ["win"]
     },
+    "components_browsertests",
     "components_unittests",
     {
       "test": "compositor_unittests",
       "platforms": ["linux", "win"]
     },
     {
       "test": "courgette_unittests",
       "platforms": ["win"]
     },
     {
@@ skipping 164 matching lines @@
   "non_filter_tests_builders": [
   ],
 
   "filter_compile_builders": [
     "win_chromium_compile_dbg",
     "win_chromium_rel_swarming",
     "win_chromium_x64_rel_swarming",
     "win8_chromium_rel"
   ]
 }