gn-build: Add tinyxml2 as a secondary source

Added tinyxml2 as a secondary source. Moved //build/secondary/testing to
//build/secondary/third_party in the process. This means that all third_party
sources (gtest, tinyxml2) should be placed in a top-level third_party directory.

BUG=21339022

Change-Id: If324ef1eb0d5061e005f62a80d23fef25e7e78a4
diff --git a/.gitignore b/.gitignore
index 21f5ccb..92b837b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,3 @@
 buildtools
 out
-# TODO(armansito): Remove this, once we resolve the gtest dependencies
-# from outside the build system.
-testing
+third_party
diff --git a/system/build/secondary/testing/gtest/BUILD.gn b/system/build/secondary/third_party/gtest/BUILD.gn
similarity index 100%
rename from system/build/secondary/testing/gtest/BUILD.gn
rename to system/build/secondary/third_party/gtest/BUILD.gn
diff --git a/system/build/secondary/third_party/tinyxml2/BUILD.gn b/system/build/secondary/third_party/tinyxml2/BUILD.gn
new file mode 100644
index 0000000..335960b
--- /dev/null
+++ b/system/build/secondary/third_party/tinyxml2/BUILD.gn
@@ -0,0 +1,23 @@
+#
+#  Copyright (C) 2015 Google, Inc.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at:
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+static_library("tinyxml2") {
+  sources = [
+    "tinyxml2.cpp"
+  ]
+
+  include_dirs = [ "." ]
+}
diff --git a/system/osi/BUILD.gn b/system/osi/BUILD.gn
index 91de6d8..abefdbc 100644
--- a/system/osi/BUILD.gn
+++ b/system/osi/BUILD.gn
@@ -71,7 +71,7 @@
 
   deps = [
     "//osi",
-    "//testing/gtest:gtest_main",
+    "//third_party/gtest:gtest_main",
   ]
 
   libs = [ "-lpthread", "-lrt" ]