Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/public/common/sandboxed_process_launcher_delegate.cc

Index: content/public/common/sandboxed_process_launcher_delegate.cc
diff --git a/content/public/common/sandboxed_process_launcher_delegate.cc b/content/public/common/sandboxed_process_launcher_delegate.cc
index e0204c48e34e864f0a25eebc47a82921b3a9c867..5435816be6d268f9a285b5b4ea3fcb4a99c07b84 100644
--- a/content/public/common/sandboxed_process_launcher_delegate.cc
+++ b/content/public/common/sandboxed_process_launcher_delegate.cc
@@ -26,9 +26,11 @@ bool SandboxedProcessLauncherDelegate::PreSpawnTarget(
 }
 
 #elif(OS_POSIX)
-bool SandboxedProcessLauncherDelegate::ShouldUseZygote() {
-  return false;
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
+ZygoteHandle* SandboxedProcessLauncherDelegate::GetZygote() {
+  return nullptr;
 }
+#endif  // !defined(OS_MACOSX) && !defined(OS_ANDROID)
 
 base::EnvironmentMap SandboxedProcessLauncherDelegate::GetEnvironment() {
   return base::EnvironmentMap();