Make CACHE_DIR set by default in most gclient configs.

recipe_modules/gclient/config.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import types
 
 from recipe_engine.config import config_item_context, ConfigGroup, BadConf
 from recipe_engine.config import ConfigList, Dict, Single, Static, Set, List
 
 from . import api as gclient_api
 
 
 def BaseConfig(USE_MIRROR=True, GIT_MODE=False, CACHE_DIR=None,
                PATCH_PROJECT=None, BUILDSPEC_VERSION=None,
                **_kwargs):
   deps = '.DEPS.git' if GIT_MODE else 'DEPS'
-  cache_dir = str(CACHE_DIR) if GIT_MODE and CACHE_DIR else None
+  cache_dir = str(CACHE_DIR) if CACHE_DIR else None

[szager1, 2016/03/08 02:24:43]

If I'm understanding this right, this is the actual fix, right?  I believe this
will also modify the deps_file gclient spec field, right?  Any concern about
that?

[iannucci, 2016/03/08 04:09:40]

It will modify it at the base of the config tree: anything else from here to the
recipe can override it.

   return ConfigGroup(
     solutions = ConfigList(
       lambda: ConfigGroup(
         name = Single(basestring),
         url = Single(basestring),
         deps_file = Single(basestring, empty_val=deps, required=False,
                            hidden=False),
         managed = Single(bool, empty_val=True, required=False, hidden=False),
         custom_deps = Dict(value_type=(basestring, types.NoneType)),
         custom_vars = Dict(value_type=basestring),
@@ skipping 614 matching lines @@
   soln = c.solutions.add()
   soln.name = 'gerrit-test-cq-normal'
   soln.url = 'https://chromium.googlesource.com/playground/gerrit-cq/normal.git'
 
 # TODO(phajdan.jr): Move to proper repo and add coverage.
 @config_ctx()
 def valgrind(c):  # pragma: no cover
   """Add Valgrind binaries to the gclient solution."""
   c.solutions[0].custom_deps['src/third_party/valgrind'] = \
     ChromiumGitURL(c, 'chromium', 'deps', 'valgrind', 'binaries')