reland #3: Set mac_min_sdk=10.10 on chromium.mac bots.

scripts/slave/recipes/chromium_trybot.expected/telemetry_gpu_no_summary.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.mac",
       "--builder",
       "mac_chromium_rel_ng",
@@ skipping 72 matching lines @@
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "GYP_DEFINES": "archive_gpu_tests=1 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1"
+      "GYP_DEFINES": "archive_gpu_tests=1 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' mac_sdk_min=10.10 target_arch=x64 test_isolation_mode=prepare use_goma=1"
     },
     "name": "gclient runhooks (with patch)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/src/testing/buildbot/chromium.mac.json",
       "/path/to/tmp/json"
@@ skipping 74 matching lines @@
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/build/gyp_chromium",
       "--analyzer",
       "{\"files\": [\"foo.cc\"], \"targets\": [\"angle_unittests_run\", \"chrome\", \"chromium_builder_tests\", \"content_gl_tests_run\", \"gl_tests_run\", \"tab_capture_end2end_tests_run\", \"telemetry_gpu_test_run\"]}",
       "/path/to/tmp/json"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
-      "GYP_DEFINES": "archive_gpu_tests=1 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1"
+      "GYP_DEFINES": "archive_gpu_tests=1 clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' mac_sdk_min=10.10 target_arch=x64 test_isolation_mode=prepare use_goma=1"
     },
     "name": "analyze",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"build_targets\": [@@@",
       "@@@STEP_LOG_LINE@json.output@    \"angle_unittests_run\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"chrome\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"chromium_builder_tests\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"content_gl_tests_run\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"gl_tests_run\", @@@",
@@ skipping 3410 matching lines @@
       "@@@STEP_FAILURE@@@",
       "@@@SET_BUILD_PROPERTY@failure_hash@\"4cd189d31a78721966a6a6d2208248a1c6db1f3a\"@@@"
     ]
   },
   {
     "name": "$final_result",
     "reason": "1 out of 1 aggregated steps failed. Failures: Step('pixel_test on Intel GPU on Mac') failed with return_code 1",
     "status_code": 1
   }
 ]