Add a component installer for Portable NaCl. Registration of installer is

chrome/common/chrome_switches.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/chrome_switches.h"
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 
 namespace switches {
@@ skipping 499 matching lines @@
 const char kEnableNTPBookmarkFeatures[]     = "enable-ntp-bookmark-features";
 
 // Enables advanced app capabilities.
 const char kEnablePlatformApps[]            = "enable-platform-apps";
 
 // Enables content settings based on host *and* plug-in in the user
 // preferences.
 const char kEnableResourceContentSettings[] =
     "enable-resource-content-settings";
 
+// Enables the installation and usage of Portable Native Client.
+const char kEnablePnacl[]                    = "enable-pnacl";

[cpu_(ooo_6.6-7.5), 2011/11/23 01:51:33]

I am not opposed to the switches idea, but you have other choices, for example
you can deploy pnacl only to canary.

Or if you are surfacing pnacl in the about:plugins page then there are even
better options. Let me know if you do.

[jvoung - send to chromium..., 2011/12/14 19:34:31]

Yes a command line doesn't seem very friendly, but I'm not sure we are ready to
enable this for all of canary yet. I'm thinking more of an internal dogfood for
now. 
I'm not really familiar with what should and should not go in about:plugins, but
PNaCl doesn't provide an additional mime handler. It's the NaCl plugin that
handles "application/x-nacl", and then may invoke PNaCl. Though it would be nice
to show the version of PNaCl somewhere for debugging.

+
 // Enables speculative TCP/IP preconnection.
 const char kEnablePreconnect[]              = "enable-preconnect";
 
 // Controls the support for SDCH filtering (dictionary based expansion of
 // content). By default SDCH filtering is enabled. To disable SDCH filtering,
 // use "--enable-sdch=0" as command line argument. SDCH is currently only
 // supported server-side for searches on google.com.
 const char kEnableSdch[]                    = "enable-sdch";
 
 // Enables the IsSearchProviderInstalled and InstallSearchProvider with an
@@ skipping 767 matching lines @@
 
 // -----------------------------------------------------------------------------
 // DO NOT ADD YOUR CRAP TO THE BOTTOM OF THIS FILE.
 //
 // You were going to just dump your switches here, weren't you? Instead, please
 // put them in alphabetical order above, or in order inside the appropriate
 // ifdef at the bottom. The order should match the header.
 // -----------------------------------------------------------------------------
 
 }  // namespace switches