Pause/Resume response content, not response

When the response content is piped through additional streams for
decoding, pause and resume calls should be propagated to the last stream
in the pipeline so that back pressure propagates correctly.

This avoids an issue where simultaneous back pressure from the content
decoding stream and from a stream to which Request is piped could cause
the response stream to get stuck waiting for a drain event on the
content decoding stream which never occurs.  See request#1567 for an example.

This commit also renames dataStream to responseContent to remedy my
previous poor choice of name, since the name will be exposed on the
Request instance it should be clearer and closer to the name used to
refer to this data in the relevant RFCs.

Fixes request#1567

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

request.js

@@ -1120,56 +1120,58 @@ Request.prototype.onRequestResponse = function (response) {
       self._ended = true
     })
 
-    var dataStream
+    var responseContent
     if (self.gzip) {
       var contentEncoding = response.headers['content-encoding'] || 'identity'
       contentEncoding = contentEncoding.trim().toLowerCase()
 
       if (contentEncoding === 'gzip') {
-        dataStream = zlib.createGunzip()
-        response.pipe(dataStream)
+        responseContent = zlib.createGunzip()
+        response.pipe(responseContent)
       } else {
         // Since previous versions didn't check for Content-Encoding header,
         // ignore any invalid values to preserve backwards-compatibility
         if (contentEncoding !== 'identity') {
           debug('ignoring unrecognized Content-Encoding ' + contentEncoding)
         }
-        dataStream = response
+        responseContent = response
       }
     } else {
-      dataStream = response
+      responseContent = response
     }
 
     if (self.encoding) {
       if (self.dests.length !== 0) {
         console.error('Ignoring encoding parameter as this stream is being piped to another stream which makes the encoding option invalid.')
-      } else if (dataStream.setEncoding) {
-        dataStream.setEncoding(self.encoding)
+      } else if (responseContent.setEncoding) {
+        responseContent.setEncoding(self.encoding)
       } else {
         // Should only occur on node pre-v0.9.4 (joyent/node@9b5abe5) with
         // zlib streams.
         // If/When support for 0.9.4 is dropped, this should be unnecessary.
-        dataStream = dataStream.pipe(stringstream(self.encoding))
+        responseContent = responseContent.pipe(stringstream(self.encoding))
       }
     }
 
+    self.responseContent = responseContent
+
     self.emit('response', response)
 
     self.dests.forEach(function (dest) {
       self.pipeDest(dest)
     })
 
-    dataStream.on('data', function (chunk) {
+    responseContent.on('data', function (chunk) {
       self._destdata = true
       self.emit('data', chunk)
     })
-    dataStream.on('end', function (chunk) {
+    responseContent.on('end', function (chunk) {
       self.emit('end', chunk)
     })
-    dataStream.on('error', function (error) {
+    responseContent.on('error', function (error) {
       self.emit('error', error)
     })
-    dataStream.on('close', function () {self.emit('close')})
+    responseContent.on('close', function () {self.emit('close')})
 
     if (self.callback) {
       var buffer = bl()
@@ -1536,18 +1538,18 @@ Request.prototype.end = function (chunk) {
 }
 Request.prototype.pause = function () {
   var self = this
-  if (!self.response) {
+  if (!self.responseContent) {
     self._paused = true
   } else {
-    self.response.pause.apply(self.response, arguments)
+    self.responseContent.pause.apply(self.responseContent, arguments)
   }
 }
 Request.prototype.resume = function () {
   var self = this
-  if (!self.response) {
+  if (!self.responseContent) {
     self._paused = false
   } else {
-    self.response.resume.apply(self.response, arguments)
+    self.responseContent.resume.apply(self.responseContent, arguments)
   }
 }
 Request.prototype.destroy = function () {