Update V8 DEPS.

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 = {
   "git_url": "https://chromium.googlesource.com",
 }
 
 deps = {
   "v8/build/gyp":
     Var("git_url") + "/external/gyp.git" + "@" + "fe00999dfaee449d3465a9316778434884da4fa7",  # from svn revision 2010
   "v8/third_party/icu":
-    Var("git_url") + "/chromium/deps/icu.git" + "@" + "53ecf0f68b27a004bef5526553b8e5f6c235b80b",
+    Var("git_url") + "/chromium/deps/icu.git" + "@" + "51c1a4ce5f362676aa1f1cfdb5b7e52edabfa5aa",
   "v8/buildtools":
     Var("git_url") + "/chromium/buildtools.git" + "@" + "4995faa4a7ad968f1fa1917c26edd5cea295582f",
   "v8/testing/gtest":
     Var("git_url") + "/external/googletest.git" + "@" + "8245545b6dc9c4703e6496d1efd19e975ad2b038",  # from svn revision 700
   "v8/testing/gmock":
     Var("git_url") + "/external/googlemock.git" + "@" + "29763965ab52f24565299976b936d1265cb6a271",  # from svn revision 501
   "v8/tools/clang":
     Var("git_url") + "/chromium/src/tools/clang.git" + "@" + "90fb65e7a9a5c9d6d9613dfb0e78921c52ca9cfc",
 }
 
@@ skipping 62 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/build/gyp_v8"],
   },
 ]