Add leakcanary to DEPS and third_party

third_party/leakcanary/leakcanary.gyp

Index: third_party/leakcanary/leakcanary.gyp
diff --git a/third_party/leakcanary/leakcanary.gyp b/third_party/leakcanary/leakcanary.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..eb143e781e7a805057eb6d3b609737cf02325313
--- /dev/null
+++ b/third_party/leakcanary/leakcanary.gyp
@@ -0,0 +1,18 @@
+# Copyright 2016 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.
+
+{
+  'targets': [
+    {
+      # Leak Canary added to GN only.
+      'target_name': 'leakcanary_java',
+      'type': 'none',
+      'variables': {
+        'java_in_dir': 'src/leakcanary-android-no-op/src/main',
+        'java_in_dir_suffix': '/java',
+      },
+      'includes': [ '../../build/java.gypi' ],
+    },
+  ],
+}