Add gclient hook to download prebuilt mojo_shell

mojo/public/tools/download_shell_binary.py

+#!/usr/bin/env python
+
+import os
+import subprocess
+import sys
+import tempfile
+import zipfile
+
+if not sys.platform.startswith("linux"):
+  print "Not supported for your platform"
+  sys.exit(0)
+
+current_path = os.path.dirname(os.path.realpath(__file__))
+version_path = os.path.join(current_path, "../VERSION")
+with open(version_path) as version_file:
+  version = version_file.read().strip()
+
+prebuilt_file_path = os.path.join(current_path, "prebuilt")
+stamp_path = os.path.join(prebuilt_file_path, "VERSION")
+
+try:
+  with open(stamp_path) as stamp_file:
+    current_version = stamp_file.read().strip()
+    if current_version == version:
+      sys.exit(0)
+except IOError:
+  pass
+
+platform = "linux-x64" # TODO: configurate
+basename = platform + ".zip"
+
+gs_path = "gs://mojo/shell/" + version + "/" + basename
+
+with tempfile.NamedTemporaryFile() as temp_zip_file:
+  subprocess.check_call(["gsutil", "cp", gs_path, temp_zip_file.name])

[jamesr, 2014/10/20 22:49:03]

this should use the gsutil binary in depot_tools - still trying to figure out
how to get that path

+  with zipfile.ZipFile(temp_zip_file.name) as z:
+    zi = z.getinfo("mojo_shell")
+    mode = zi.external_attr >> 16L
+    z.extract(zi, prebuilt_file_path)
+    os.chmod(os.path.join(prebuilt_file_path, "mojo_shell"), mode)
+
+with open(stamp_path, 'w') as stamp_file:
+  stamp_file.write(version + "\n")