Revert "Expand variables in gclient flattened output."

This reverts commit a32f98e652d5e151f70d571cf046c3d83ae2f486.

Reason for revert:
Doesn't work when there are variables which definition includes other variables, e.g.:

'cros_download_vm': '"{cros_board}" == "amd64_generic"',

Original change's description:
> Expand variables in gclient flattened output.
> 
> Bug: 848990
> Change-Id: I0ad7e4f965973edbc5a335bd30f9cbd7b04abff2
> Reviewed-on: https://chromium-review.googlesource.com/1085996
> Reviewed-by: Michael Moss <mmoss@chromium.org>
> Reviewed-by: Aaron Gable <agable@chromium.org>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

TBR=agable@chromium.org,mmoss@chromium.org,ehmaldonado@chromium.org

Change-Id: I7e81000e92aa352e45b420845bb1dcc8572f1962
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 848990
Reviewed-on: https://chromium-review.googlesource.com/1085974
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
diff --git a/roll_dep.py b/roll_dep.py
index 82331a8..982d533 100755
--- a/roll_dep.py
+++ b/roll_dep.py
@@ -225,7 +225,7 @@
     # First gather all the information without modifying anything, except for a
     # git fetch.
     deps_path, deps_content = get_deps(current_dir)
-    gclient_dict = gclient_eval.Exec(deps_content, deps_path)
+    gclient_dict = gclient_eval.Exec(deps_content, True, deps_path)
     is_relative = gclient_dict.get('use_relative_paths', False)
     root_dir = current_dir if is_relative else gclient_root
     rolls = {}