Fix incorrect map usage in the WebPluginImpl::didReceiveData function, which ...

Fix incorrect map usage in the WebPluginImpl::didReceiveData function, which caused
a response to be incorrectly treated as a multipart response. This would eventually
end up sending the ViewHostMsg_DidStopLoading IPC to the browser, which would treat the
page as loaded, when it has not. 

This fixes http://code.google.com/p/chromium/issues/detail?id=7916, which would cause
the favicon to not show up on trunk.

Bug=7916
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=10499

[amit, 2009-02-26 19:08:20]

lgtm