Remove the --allow-no-sandbox-job flag in favor of automatic recognition.

content/common/sandbox_win.cc

Index: content/common/sandbox_win.cc
diff --git a/content/common/sandbox_win.cc b/content/common/sandbox_win.cc
index 6dee6e96a96299cd3aa01a46772f727c46ec6bf4..a3b954e063f24847e6bc7cddee27c12cb9bab4da 100644
--- a/content/common/sandbox_win.cc
+++ b/content/common/sandbox_win.cc
@@ -251,9 +251,6 @@ base::string16 PrependWindowsSessionPath(const base::char16* object) {
 
 // Checks if the sandbox should be let to run without a job object assigned.
 bool ShouldSetJobLevel(const base::CommandLine& cmd_line) {
-  if (!cmd_line.HasSwitch(switches::kAllowNoSandboxJob))
-    return true;
-
   // Windows 8 allows nested jobs so we don't need to check if we are in other
   // job.
   if (base::win::GetVersion() >= base::win::VERSION_WIN8)
@@ -277,6 +274,20 @@ bool ShouldSetJobLevel(const base::CommandLine& cmd_line) {
   if (job_info.BasicLimitInformation.LimitFlags & JOB_OBJECT_LIMIT_BREAKAWAY_OK)
     return true;
 
+  // Lastly in place of the flag which was supposed to be used only for running
+  // Chrome in remote sessions we do this check explicitly here.
+  // According to MS this flag can be false for a remote session only on Windows
+  // Server 2012 and newer so if we do the check last we should be on the safe
+  // side. See: https://msdn.microsoft.com/en-us/library/aa380798.aspx.
+  if (!::GetSystemMetrics(SM_REMOTESESSION)) {
+    // TODO(pastarmovj): Remove this check and the flag altogether once we are
+    // convinced that the automatic logic is good enough.
+    return !cmd_line.HasSwitch(switches::kAllowNoSandboxJob);
+  }
+
+  // Allow running without the sandbox in this case. This slightly reduces the
+  // ability of the sandbox to protect its children from spawning new processes
+  // or preventing them from shutting down Windows or accessing the clipboard.
   return false;
 }
 
@@ -570,7 +581,9 @@ sandbox::ResultCode SetJobLevel(const base::CommandLine& cmd_line,
                                 sandbox::JobLevel job_level,
                                 uint32_t ui_exceptions,
                                 sandbox::TargetPolicy* policy) {
-  if (!ShouldSetJobLevel(cmd_line))
+  const bool should_set_job = ShouldSetJobLevel(cmd_line);
+  UMA_HISTOGRAM_BOOLEAN("Process.Sandbox.ShouldSetJobNone", should_set_job);

[Will Harris, 2017/02/16 23:48:17]

I feel like I'm being a terrible reviewer here and making you go round in
circles but I think the point of having the UMA histogram is to detect the times
when

 - enterprise is using --allow-no-sandbox-job
 - had they not used this switch, then the sandbox would not have correctly
worked.

I think the code right now just reports when --allow-no-sandbox-job is being
used, but not when it would have worked had it not been used.

+  if (!should_set_job)
     return policy->SetJobLevel(sandbox::JOB_NONE, 0);
 
 #ifdef _WIN64