Add a command line flag to change the default number of parallel DNS requests...

Add a command line flag to change the default number of parallel DNS requests issued by chrome.

  --host-resolver-parallelism=XXX

This is a useful debugging tool, since for some users too many parallel DNS requests results in spurious DNS failures from their resolver.

BUG=44489
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=52802

[jar (doing other things), 2010-07-17 00:31:11]

LGTM... but there is a nit and a comment.

I didn't like the zero... but I probably won't like the longer lines for using a
manifest constant... but I think it might be more readable.  You can make the
call on the comment.

http://codereview.chromium.org/3019007/diff/1/3
File chrome/common/chrome_switches.cc (right):

http://codereview.chromium.org/3019007/diff/1/3#newcode517
chrome/common/chrome_switches.cc:517: const char kHostResolverParallelism[]     
 = "host-resolver-parallelism";
nit: Move in front of line 512 to alphabetize.

http://codereview.chromium.org/3019007/diff/1/4
File chrome/common/chrome_switches.h (right):

http://codereview.chromium.org/3019007/diff/1/4#newcode156
chrome/common/chrome_switches.h:156: extern const char
kHostResolverParallelism[];
nit: move up one line to alphabetize.

http://codereview.chromium.org/3019007/diff/1/8
File net/base/host_resolver.h (right):

http://codereview.chromium.org/3019007/diff/1/8#newcode241
net/base/host_resolver.h:241: // If |max_concurrent_resolves| is 0 then the
default level of parallelism will
comment/question/suggestion: I didn't like seeing the zero being passed in, as I
would have had no idea what the argument meant.  How about defining:
HostResolver::kDefaultParallism == 0 and using when needed at call sites?

[eroman, 2010-07-17 00:57:20]

Thanks for the fast review!

http://codereview.chromium.org/3019007/diff/1/3
File chrome/common/chrome_switches.cc (right):

http://codereview.chromium.org/3019007/diff/1/3#newcode517
chrome/common/chrome_switches.cc:517: const char kHostResolverParallelism[]     
 = "host-resolver-parallelism";
On 2010/07/17 00:31:11, jar wrote:
> nit: Move in front of line 512 to alphabetize.

Done.

http://codereview.chromium.org/3019007/diff/1/8
File net/base/host_resolver.h (right):

http://codereview.chromium.org/3019007/diff/1/8#newcode241
net/base/host_resolver.h:241: // If |max_concurrent_resolves| is 0 then the
default level of parallelism will
On 2010/07/17 00:31:11, jar wrote:
> comment/question/suggestion: I didn't like seeing the zero being passed in, as
I
> would have had no idea what the argument meant.  How about defining:
> HostResolver::kDefaultParallism == 0 and using when needed at call sites?

Done.

[jar (doing other things), 2010-07-17 01:13:55]

LGTM