Add a PORT parameter to make serve command in the NaCl SDK Makefile.

native_client_sdk/src/doc/Makefile

 # Makefile for Sphinx documentation
 #
 
 # You can set these variables from the command line.
 SPHINXOPTS    = -W
 SPHINXBUILD   = sphinx-build
 BUILDDIR      = _build
 CHROMESITE_BUILDDIR = $(realpath ../../doc_generated)
+PORT = 8000
 
 # User-friendly check for sphinx-build
 ifeq ($(shell which $(SPHINXBUILD) >/dev/null 2>&1; echo $$?), 1)
 $(error The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the '$(SPHINXBUILD)' executable. Alternatively you can add the directory with the executable to your PATH. If you don't have Sphinx installed, grab it from http://sphinx-doc.org/)
 endif
 
 # Internal variables.
 ALLSPHINXOPTS   = -d $(BUILDDIR)/doctrees $(SPHINXOPTS) .
 
 .PHONY: all help clean linkcheck doctest chromesite chromesite_rst serve
@@ skipping 43 matching lines @@
         -rm $(CHROMESITE_BUILDDIR)/.buildinfo
         $(SPHINXBUILD) -b chromesite $(ALLSPHINXOPTS) $(CHROMESITE_BUILDDIR)
         rm -rf $(CHROMESITE_BUILDDIR)/images
         cp -r $(CHROMESITE_BUILDDIR)/_images $(CHROMESITE_BUILDDIR)/images
         rm -rf $(CHROMESITE_BUILDDIR)/{_images,searchindex.js}
 
 presubmit:
         -rm $(BUILDDIR)/.buildinfo
         $(SPHINXBUILD) -b chromesite $(ALLSPHINXOPTS) $(BUILDDIR)
 
-serve:
-        ../../../chrome/common/extensions/docs/server2/preview.py
+serve: chromesite_rst
+        ../../../chrome/common/extensions/docs/server2/preview.py -p $(PORT)