Fix autoroller in accordance to upstream change

tools_webrtc/autoroller/roll_deps.py

Index: tools_webrtc/autoroller/roll_deps.py
diff --git a/tools_webrtc/autoroller/roll_deps.py b/tools_webrtc/autoroller/roll_deps.py
index 2d8bd721a718fe12a0a1461b9db97faf6093c94a..b96102985f235acbcacc784d2448f7fc307a39bf 100755
--- a/tools_webrtc/autoroller/roll_deps.py
+++ b/tools_webrtc/autoroller/roll_deps.py
@@ -50,7 +50,6 @@ CHECKOUT_ROOT_DIR = os.path.realpath(os.path.join(CHECKOUT_SRC_DIR, os.pardir))
 sys.path.append(os.path.join(CHECKOUT_SRC_DIR, 'build'))
 import find_depot_tools
 find_depot_tools.add_depot_tools_to_path()
-from gclient import GClientKeywords
 
 CLANG_UPDATE_SCRIPT_URL_PATH = 'tools/clang/scripts/update.py'
 CLANG_UPDATE_SCRIPT_LOCAL_PATH = os.path.join(CHECKOUT_SRC_DIR, 'tools',
@@ -64,11 +63,14 @@ class RollError(Exception):
   pass
 
 
+def VarLookup(local_scope):
+  return lambda var_name: local_scope['vars'][var_name]
+
+
 def ParseDepsDict(deps_content):
   local_scope = {}
-  var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'Var': var.Lookup,
+    'Var': VarLookup(local_scope),
     'deps_os': {},
   }
   exec(deps_content, global_scope, local_scope)