Add accessibility_unittests and chromevox_tests to buildbot config.

testing/buildbot/chromium.mac.json

Index: testing/buildbot/chromium.mac.json
diff --git a/testing/buildbot/chromium.mac.json b/testing/buildbot/chromium.mac.json
index bb4b7a4a7c3b36307ebf187e7c14ab2a183d5a13..6202ceaf5c921fd8166e9b00d2c554b136434d2d 100644
--- a/testing/buildbot/chromium.mac.json
+++ b/testing/buildbot/chromium.mac.json
@@ -2,6 +2,7 @@
   "Mac10.6 Tests (1)": {
     "gtest_tests": [
       "interactive_ui_tests",
+      "accessibility_unittests",
       "base_unittests",
       "cacheinvalidation_unittests",
       "cast_unittests",
@@ -56,6 +57,7 @@
   "Mac10.7 Tests (1)": {
     "gtest_tests": [
       "interactive_ui_tests",
+      "accessibility_unittests",
       "base_unittests",
       "cacheinvalidation_unittests",
       "cast_unittests",
@@ -137,6 +139,7 @@
   "Mac 10.6 Tests (dbg)(3)": {
     "gtest_tests": [
       "interactive_ui_tests",
+      "accessibility_unittests",
       "base_unittests",
       {"test": "browser_tests", "shard_index": 2, "total_shards": 4}
     ]
@@ -195,6 +198,7 @@
   "Mac 10.7 Tests (dbg)(3)": {
     "gtest_tests": [
       "interactive_ui_tests",
+      "accessibility_unittests",
       "base_unittests",
       {"test": "browser_tests", "shard_index": 2, "total_shards": 4}
     ]