Fix a bunch of pyauto tests

chrome/test/automation/proxy_launcher.cc

Index: chrome/test/automation/proxy_launcher.cc
diff --git a/chrome/test/automation/proxy_launcher.cc b/chrome/test/automation/proxy_launcher.cc
index d387aefc32118fa6630bb475cf06a37b75633399..895a2d0afc1211321822665d1830e9888c2e07a9 100644
--- a/chrome/test/automation/proxy_launcher.cc
+++ b/chrome/test/automation/proxy_launcher.cc
@@ -426,6 +426,9 @@ void ProxyLauncher::PrepareTestCommandline(CommandLine* command_line,
 
   // Allow file:// access on ChromeOS.
   command_line->AppendSwitch(switches::kAllowFileAccess);
+
+  // The tests assume that file:// URIs can freely access other file:// URIs.
+  command_line->AppendSwitch(switches::kAllowFileAccessFromFiles);
 }
 
 bool ProxyLauncher::LaunchBrowserHelper(const LaunchState& state,