Try ICU 59-to-be with UChar being char16_t everywhere

DEPS

 # Note: The buildbots evaluate this file with CWD set to the parent
 # directory and assume that the root of the checkout is in ./v8/, so
 # all paths in here must match this assumption.
 
 vars = {
   "chromium_url": "https://chromium.googlesource.com",
 }
 
 deps = {
   "v8/build":
     Var("chromium_url") + "/chromium/src/build.git" + "@" + "957a0ba4d6375e502c04e8099bec7ef8e11d0efe",
   "v8/tools/gyp":
     Var("chromium_url") + "/external/gyp.git" + "@" + "e7079f0e0e14108ab0dba58728ff219637458563",
   "v8/third_party/icu":
-    Var("chromium_url") + "/chromium/deps/icu.git" + "@" + "450be73c9ee8ae29d43d4fdc82febb2a5f62bfb5",
+    Var("chromium_url") + "/chromium/deps/icu.git" + "@" + "4960d136ae73a60b41ccfbfa02440d2068b80280",
   "v8/third_party/instrumented_libraries":
     Var("chromium_url") + "/chromium/src/third_party/instrumented_libraries.git" + "@" + "62275386c19e927797e8ae6b0c6e57a76c9c6f3c",
   "v8/buildtools":
     Var("chromium_url") + "/chromium/buildtools.git" + "@" + "b3771b1935ea74c388b6fb1750e83f5d83b39dec",
   "v8/base/trace_event/common":
     Var("chromium_url") + "/chromium/src/base/trace_event/common.git" + "@" + "06294c8a4a6f744ef284cd63cfe54dbf61eea290",
   "v8/third_party/jinja2":
     Var("chromium_url") + "/chromium/src/third_party/jinja2.git" + "@" + "d34383206fa42d52faa10bb9931d6d538f3a57e0",
   "v8/third_party/markupsafe":
     Var("chromium_url") + "/chromium/src/third_party/markupsafe.git" + "@" + "8f45f5cfa0009d2a70589bcda0349b8cb2b72783",
@@ skipping 264 matching lines @@
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "v8/gypfiles/gyp_v8", "--running-as-hook"],
   },
 ]