gclient hook that downloads go binaries

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/1092363006
diff --git a/DEPS b/DEPS
index bb3bb3a..1f7f73e 100644
--- a/DEPS
+++ b/DEPS
@@ -338,5 +338,14 @@
         '--packages', 'pnacl_newlib',
         'sync', '--extract',
     ],
-  }
+  },
+  {
+    # This downloads linux and android Go binaries according to
+    # tools/go/VERSION.
+    'name': 'gotools',
+    'pattern': '.',
+    'action': [
+        'python', 'src/tools/go/download.py',
+    ],
+  },
 ]