Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/public/common/sandboxed_process_launcher_delegate.h

Index: content/public/common/sandboxed_process_launcher_delegate.h
diff --git a/content/public/common/sandboxed_process_launcher_delegate.h b/content/public/common/sandboxed_process_launcher_delegate.h
index a3aa4e06426534344883bdab2be7fe60536a296d..fdf5f5825b4d9919eb3a4c68e3dc6cf32989ccb2 100644
--- a/content/public/common/sandboxed_process_launcher_delegate.h
+++ b/content/public/common/sandboxed_process_launcher_delegate.h
@@ -22,6 +22,13 @@ class TargetPolicy;
 
 namespace content {
 
+#if defined(OS_LINUX)
+class ZygoteCommunication;
+using ZygoteHandle = ZygoteCommunication*;
+#else
+using ZygoteHandle = std::nullptr_t;
+#endif
+
 // Allows a caller of StartSandboxedProcess or
 // BrowserChildProcessHost/ChildProcessLauncher to control the sandbox policy,
 // i.e. to loosen it if needed.
@@ -51,8 +58,10 @@ class CONTENT_EXPORT SandboxedProcessLauncherDelegate {
   virtual void PostSpawnTarget(base::ProcessHandle process) {}
 
 #elif defined(OS_POSIX)
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
   // Override this to return true to use the setuid sandbox.
-  virtual bool ShouldUseZygote();
+  virtual ZygoteHandle* GetZygote();
+#endif  // !defined(OS_MACOSX) && !defined(OS_ANDROID)
 
   // Override this if the process needs a non-empty environment map.
   virtual base::EnvironmentMap GetEnvironment();