Add a switch for changing the fd limit on Mac/Linux....

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
===================================================================
--- chrome/common/chrome_switches.cc	(revision 18429)
+++ chrome/common/chrome_switches.cc	(working copy)
@@ -504,4 +504,9 @@
 // is to be used only by the upgrade process.
 const wchar_t kTryChromeAgain[]      = L"try-chrome-again";
 
+// The file descriptor limit is set to the value of this switch, subject to the
+// OS hard limits. Useful for testing that file descriptor exhaustion is handled
+// gracefully.
+const wchar_t kFileDescriptorLimit[]           = L"file-descriptor-limit";
+
 }  // namespace switches