Add Clang ToT builder for iOS

scripts/slave/recipes/chromium.expected/full_chromium_fyi_ClangToTiOS.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.fyi",
       "--builder",
-      "Chromium iOS Device (ninja)",
+      "ClangToTiOS",
       "--slave",
       "TestSlavename",
       "--spec",
       "cache_dir = '[ROOT]/git_cache'\nsolutions = [{'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'https://chromium.googlesource.com/chromium/blink.git'}, 'deps_file': '.DEPS.git', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}, {'custom_deps': {'src/chrome/test/data/firefox2_profile/searchplugins': None, 'src/chrome/test/data/firefox2_searchplugins': None, 'src/chrome/test/data/firefox3_profile/searchplugins': None, 'src/chrome/test/data/firefox3_searchplugins': None, 'src/chrome/test/data/osdd': None, 'src/chrome/test/data/perf/frame_rate/private': None, 'src/chrome/test/data/plugin': None, 'src/chrome/test/data/ssl/certs': None, 'src/data/autodiscovery': None, 'src/data/esctf': None, 'src/data/mach_ports': None, 'src/data/memory_test': None, 'src/data/mozilla_js_tests': None, 'src/data/page_cycler': None, 'src/data/selenium_core': None, 'src/data/tab_switching': None, 'src/tools/grit/grit/test/data': None, 'src/webkit/data/bmp_decoder': None, 'src/webkit/data/ico_decoder': None, 'src/webkit/data/test_shell/plugins': None, 'src/webkit/data/xbm_decoder': None}, 'deps_file': '.DEPS.git', 'managed': True, 'name': 'src-internal', 'url': 'https://chrome-internal.googlesource.com/chrome/src-internal.git'}]\ntarget_os = ['ios']",
       "--root",
       "src",
       "--revision_mapping_file",
       "{\"src\": \"got_revision\", \"src/native_client\": \"got_nacl_revision\", \"src/third_party/WebKit\": \"got_webkit_revision\", \"src/third_party/webrtc\": \"got_webrtc_revision\", \"src/tools/swarming_client\": \"got_swarming_client_revision\", \"src/v8\": \"got_v8_revision\"}",
       "--output_json",
       "/path/to/tmp/json",
@@ skipping 43 matching lines @@
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "GYP_CROSSCOMPILE": "1",
-      "GYP_DEFINES": "OS=ios chromium_ios_signing=0 clang_xcode=0 component=static_library target_subarch=both",
+      "GYP_DEFINES": "OS=ios chromium_ios_signing=0 clang_use_chrome_plugins=0 clang_xcode=0 component=static_library werror=''",
       "GYP_GENERATORS": "ninja",
-      "GYP_GENERATOR_FLAGS": "xcode_project_version=3.2"
+      "GYP_GENERATOR_FLAGS": "xcode_project_version=3.2",
+      "LLVM_FORCE_HEAD_REVISION": "YES"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/src/testing/buildbot/chromium.fyi.json",
       "/path/to/tmp/json"
@@ skipping 12 matching lines @@
       "-u",
       "[SLAVE_BUILD]/src/testing/scripts/get_compile_targets.py",
       "--output",
       "/path/to/tmp/json",
       "--",
       "--build-config-fs",
       "Release-iphoneos",
       "--paths",
       "{\"build\": \"[BUILD]\", \"checkout\": \"[SLAVE_BUILD]/src\"}",
       "--properties",
-      "{\"buildername\": \"Chromium iOS Device (ninja)\", \"buildnumber\": 571, \"mastername\": \"chromium.fyi\", \"slavename\": \"TestSlavename\", \"target_platform\": \"ios\"}"
+      "{\"buildername\": \"ClangToTiOS\", \"buildnumber\": 571, \"mastername\": \"chromium.fyi\", \"slavename\": \"TestSlavename\", \"target_platform\": \"ios\"}"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
@@ skipping 12 matching lines @@
       "--target",
       "Release-iphoneos",
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--build-tool",
       "ninja",
       "--",
       "All"
     ],
     "cwd": "[SLAVE_BUILD]",
+    "env": {
+      "LLVM_FORCE_HEAD_REVISION": "YES"
+    },
     "name": "compile"
   }
 ]