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":
-    Var("git_url") + "/chromium/src/build.git" + "@" + "76e9bd0241b00735b5bc402c926d7cb141a726ef",
+    Var("git_url") + "/chromium/src/build.git" + "@" + "6b34ef332946c38d33d0c08c1915d4b392808ebb",
   "v8/tools/gyp":
     Var("git_url") + "/external/gyp.git" + "@" + "bce1c7793010574d88d7915e2d55395213ac63d1",
   "v8/third_party/icu":
     Var("git_url") + "/chromium/deps/icu.git" + "@" + "ffa4b6704cf5cc9fec9485731f24a05b2ba94bca",
   "v8/buildtools":
     Var("git_url") + "/chromium/buildtools.git" + "@" + "3780bc523aad1d68a5bd00e05c453a80b2ba0b35",
   "v8/base/trace_event/common":
     Var("git_url") + "/chromium/src/base/trace_event/common.git" + "@" + "54b8455be9505c2cb0cf5c26bb86739c236471aa",
   "v8/tools/mb":
-    Var('git_url') + '/chromium/src/tools/mb.git' + '@' + "bc05800a7cd7833ad7c2d1423cd8b2153470c9bd",
+    Var('git_url') + '/chromium/src/tools/mb.git' + '@' + "340ee1614f0ab8aa8b1846d10b26426789dbca0e",
   "v8/tools/swarming_client":
     Var('git_url') + '/external/swarming.client.git' + '@' + "df6e95e7669883c8fe9ef956c69a544154701a49",
   "v8/testing/gtest":
     Var("git_url") + "/external/github.com/google/googletest.git" + "@" + "6f8a66431cb592dad629028a50b3dd418a408c87",
   "v8/testing/gmock":
     Var("git_url") + "/external/googlemock.git" + "@" + "0421b6f358139f02e102c9c332ce19a33faf75be",
   "v8/test/benchmarks/data":
     Var("git_url") + "/v8/deps/third_party/benchmarks.git" + "@" + "05d7188267b4560491ff9155c5ee13e207ecd65f",
   "v8/test/mozilla/data":
     Var("git_url") + "/v8/deps/third_party/mozilla-tests.git" + "@" + "f6c578a10ea707b1a8ab0b88943fe5115ce2b9be",
@@ skipping 203 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"],
   },
 ]