Merge branch 'master' into storage_issue_170

Author: HemangChothani

google/cloud/storage/client.py

@@ -932,7 +932,7 @@ def generate_signed_post_policy_v4(
  credentials=None,
  virtual_hosted_style=False,
  bucket_bound_hostname=None,
- scheme=None,
+ scheme="http",
  service_account_email=None,
  access_token=None,
  ):