drop depot_tools dependency in bin/fetch-gn

... and copy gn to bin/ when done to make it easy to find.

Change-Id: I1ec405b4c45efb828626ff7d904a417f69b39cb2
Reviewed-on: https://skia-review.googlesource.com/6962
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/bin/fetch-gn b/bin/fetch-gn
index fc2c82a..16e2875 100755
--- a/bin/fetch-gn
+++ b/bin/fetch-gn
@@ -5,12 +5,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import subprocess
+import os
+import shutil
+import stat
 import sys
-
-def quiet(*cmd):
-  cmd = ' '.join(cmd).split()
-  subprocess.check_output(cmd)
+import urllib2
 
 def gn_path():
   if 'linux' in sys.platform:
@@ -19,11 +18,12 @@
     return 'buildtools/mac/gn'
   return 'buildtools/win/gn.exe'
 
-def download_tool():
-	if 'linux' in sys.platform or 'darwin' in sys.platform:
-		return 'download_from_google_storage'
-	return 'download_from_google_storage.bat'
-	 
-quiet(download_tool(),
-      '--no_resume --no_auth --bucket chromium-gn',
-      '-s ', gn_path() + '.sha1')
+sha1 = open(gn_path() + '.sha1').read()
+
+with open(gn_path(), 'wb') as f:
+    f.write(urllib2.urlopen('https://chromium-gn.storage-download.googleapis.com/' + sha1).read())
+
+os.chmod(gn_path(), stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
+                    stat.S_IRGRP                | stat.S_IXGRP |
+                    stat.S_IROTH                | stat.S_IXOTH )
+shutil.copy(gn_path(), 'bin');