Depend on v8:v8 instead of v8:mksnapshot

BUG=none
R=brettw@chromium.org

Review URL: https://codereview.chromium.org/302783009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274198 0039d316-1c4b-4281-b951-d872f2087c98

BUILD.gn

@@ -85,7 +85,7 @@ group("root") {
     "//ui/strings",
     "//ui/surface",
     "//url",
-    "//v8:mksnapshot",
+    "//v8:v8",
     "//webkit/browser:storage",
     "//webkit/child",
   ]