Add support for Mac vs. Linux sky_server builds

I also made sky_server get pulled down via DEPS
since thats how all the rest of our google storage-based
binaries work.

R=jamesr@chromium.org, jackson@google.com
TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/1150033006
diff --git a/DEPS b/DEPS
index 9f5ba68..5133110 100644
--- a/DEPS
+++ b/DEPS
@@ -251,6 +251,29 @@
                 '-s', 'src/buildtools/mac/clang-format.sha1',
     ],
   },
+  # Pull sky_server binaries using checked-in hashes.
+  {
+    'name': 'sky_server_linux',
+    'pattern': '.',
+    'action': [ 'download_from_google_storage',
+                '--no_resume',
+                '--platform=linux*',
+                '--no_auth',
+                '--bucket', 'mojo',
+                '-s', 'src/sky/tools/skygo/linux64/sky_server.sha1',
+    ],
+  },
+  {
+    'name': 'sky_server_mac',
+    'pattern': '.',
+    'action': [ 'download_from_google_storage',
+                '--no_resume',
+                '--platform=darwin',
+                '--no_auth',
+                '--bucket', 'mojo',
+                '-s', 'src/sky/tools/skygo/mac/sky_server.sha1',
+    ],
+  },
   # Pull binutils for linux, enabled debug fission for faster linking /
   # debugging when used with clang on Ubuntu Precise.
   # https://code.google.com/p/chromium/issues/detail?id=352046