Split NaCl SFI and non-SFI helpers into separate processes

chrome/app/chrome_main_delegate.cc

Index: chrome/app/chrome_main_delegate.cc
diff --git a/chrome/app/chrome_main_delegate.cc b/chrome/app/chrome_main_delegate.cc
index 486cd42220d210c531f6fcaaa862f7ffb5dffb0e..ea2b07fa41cadc0ac3000d4520cb097be68e524b 100644
--- a/chrome/app/chrome_main_delegate.cc
+++ b/chrome/app/chrome_main_delegate.cc
@@ -858,7 +858,8 @@ bool ChromeMainDelegate::DelaySandboxInitialization(
 void ChromeMainDelegate::ZygoteStarting(
     ScopedVector<content::ZygoteForkDelegate>* delegates) {
 #if !defined(DISABLE_NACL)
-  delegates->push_back(new NaClForkDelegate());
+  delegates->push_back(new NaClForkDelegate(false /* nonsfi_mode */));
+  delegates->push_back(new NaClForkDelegate(true /* nonsfi_mode */));

[Mark Seaborn, 2014/05/09 22:44:48]

This will launch an extra process at browser startup on machines that don't need
it.

It would be nice to avoid that overhead.  Can we make this conditional, please,
so that it only happens if:

defined(OS_CHROMEOS) && defined(ARCH_CPU_ARMEL)
OR
cmd_line->HasSwitch(switches::kEnableNaClNonSfiMode)

-- following the conditionals Elijah is adding in
https://codereview.chromium.org/264923011/.  (Specifically in
https://codereview.chromium.org/264923011/diff/170001/components/nacl/browser...)

[jln (very slow on Chromium), 2014/05/09 22:59:28]

Good point, but let's make sure that we don't duplicate this logic (which should
live in components/nacl/, once).

[mdempsky, 2014/05/09 23:49:35]

Mark and I chatted about this over IM, and I believe the new patch set (#4)
addresses his concerns.

I still unconditionally add the non-SFI delegate, but now I avoid launching the
helper process in Init() unless its actually needed/enabled.  The main upside
(IMO) to this is if components/nacl erroneously tries to launch a non-sfi
process, we won't fallback to the default zygote fork() logic.

I also went ahead and moved this code into components/nacl/app so we can easily
iterate on it in the future without needing to pester any chrome/app OWNERS.

 #endif
 }