HTTPTransport.Upload33k failed on Windows due to WinHTTP timing out. The
test server, http_transport_test_server.py, writes the entire request to
a stdout pipe, to be received by crashpad_util_test. crashpad_util_test
is also the HTTP client, and it does not attempt to read from this pipe
until the HTTP transaction is complete. http_transport_test_server.py
must not write to stdout until the transaction is complete, otherwise,
there is a risk of deadlock if the pipe buffer fills up. The new
Upload33k test sends a large request, which was filling up the pipe
buffer on Windows.
This also adds an Upload33k_LengthUnknown test variant to exercise a
large POST when the length is not known ahead of time. This more closely
matches how Crashpad crash uploads are done on OS X.
TEST=crashpad_util_test HTTPTransport.*
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/1286173007 .
