Fix stack limit exceeded in http client.
Fix stack limit exceeded in http client.

R=henrike@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/23419004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f7e5f22f98346bb19ca9ac7ea3912fea5b13131c

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc