Move the bits of Prefs where production code has only trivially easy

DEPS

 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 
 vars = {
   # Use this googlecode_url variable only if there is an internal mirror for it.
   # If you do not know, use the full path while defining your new deps entry.
   "googlecode_url": "http://%s.googlecode.com/svn",
   "sourceforge_url": "http://%(repo)s.svn.sourceforge.net/svnroot/%(repo)s",
   "webkit_trunk": "http://svn.webkit.org/repository/webkit/trunk",
   "nacl_trunk": "http://src.chromium.org/native_client/trunk",
@@ skipping 551 matching lines @@
   # Everybody can use some things.
   "+base",
   "+build",
   "+googleurl",
   "+ipc",
 
   # For now, we allow ICU to be included by specifying "unicode/...", although
   # this should probably change.
   "+unicode",
   "+testing",
+
+  # Until we finish breaking dependencies of base/prefs back to chrome/,
+  # don't try to use it (unless you're in chrome/).
+  "-base/prefs",
 ]
 
 
 # checkdeps.py shouldn't check include paths for files in these dirs:
 skip_child_includes = [
   "breakpad",
   "chrome_frame",
   "delegate_execute",
   "metro_driver",
   "native_client_sdk",
@@ skipping 40 matching lines @@
     "pattern": ".",
     "action": ["python", "src/build/util/lastchange.py",
                "-o", "src/build/util/LASTCHANGE"],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
 ]