Add dummy DEPS file for googletest.

This will allow clients that use the subtree mirror to specify a
revision for GoogleTest without needing nested DEPS.

Also cleans up the gitignore for the subtree mirror so gclient
revert will work properly.

Bug: 1017514
Change-Id: I17f6e1299c62b9a4cc4b7726501a9d6cf599ac9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1877597Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709196}

third_party/.gitignore

@@ -95,7 +95,6 @@
 /google_appengine_cloudstorage
 /google_toolbox_for_mac/src
 /googlemac
-/googletest/src
 /grpc/src
 /gson/lib/
 /gvr-android-sdk/common_library.aar

third_party/googletest/.gitignore

+/src

third_party/googletest/DEPS

+# This file is a dummy used so that non-Chromium clients can specify
+# recursive DEPS. Otherwise the clients would need to nest DEPS inside
+# each other. Nested DEPS are not supported by gclient.
+#
+# Clients *must* specify googletest_revision when using this DEPS file.
+
+use_relative_paths = True
+
+vars = {
+  'chromium_git': 'https://chromium.googlesource.com',
+
+  # We must specify a dummy variable here for recursedeps to work.
+  'googletest_revision': 'master',
+}
+
+deps = {
+  'src': '{chromium_git}/external/github.com/google/googletest.git@{googletest_revision}'
+}