child_process: get rid of forEach() and slice() in IPC

lib/internal/child_process.js

@@ -447,19 +447,19 @@ function setupChannel(target, channel) {
     // TODO(bnoordhuis) Check that nread > 0.
     if (pool) {
       // Linebreak is used as a message end sign
-      var lines = decoder.write(pool).split('\n');
-      var chunks = lines.slice(0, -1);
+      var chunks = decoder.write(pool).split('\n');
+      var numCompleteChunks = chunks.length - 1;
       // Last line does not have trailing linebreak
-      var incompleteChunk = lines[lines.length - 1];
-      if (chunks.length === 0) {
+      var incompleteChunk = chunks[numCompleteChunks];
+      if (numCompleteChunks === 0) {
         jsonBuffer += incompleteChunk;
         this.buffering = jsonBuffer.length !== 0;
         return;
       }
       chunks[0] = jsonBuffer + chunks[0];
 
-      chunks.forEach(function(json) {
-        var message = JSON.parse(json);
+      for (var i = 0; i < numCompleteChunks; i++) {
+        var message = JSON.parse(chunks[i]);
 
         // There will be at most one NODE_HANDLE message in every chunk we
         // read because SCM_RIGHTS messages don't get coalesced. Make sure
@@ -468,7 +468,7 @@ function setupChannel(target, channel) {
           handleMessage(target, message, recvHandle);
         else
           handleMessage(target, message, undefined);
-      });
+      }
       jsonBuffer = incompleteChunk;
       this.buffering = jsonBuffer.length !== 0;