Use a single, generic, global zygote to temporarily resolve perf regressions.

content/browser/zygote_host/zygote_handle_linux.cc

Index: content/browser/zygote_host/zygote_handle_linux.cc
diff --git a/content/browser/zygote_host/zygote_handle_linux.cc b/content/browser/zygote_host/zygote_handle_linux.cc
index 89adc49385b4364803f4cd14fc64a4e7fbfa25d6..8aaa03130fe2000f1d6653008d94ac89a0edf8dc 100644
--- a/content/browser/zygote_host/zygote_handle_linux.cc
+++ b/content/browser/zygote_host/zygote_handle_linux.cc
@@ -14,4 +14,9 @@ ZygoteHandle CreateZygote() {
   return zygote;
 }
 
+ZygoteHandle GetGenericZygote() {

[mdempsky, 2016/01/28 23:25:40]

Change to:

  ZygoteHandle* GetGenericZygote() {
    static ZygoteHandle zygote;
    return &zygote;
  }

so all of the SandboxedProcessLauncherDelegate::GetZygote() overloads become
something like

  ZygoteHandle* FooDelegate::GetZygote() {
    return content::GetGenericZygote();
  }

[Greg K, 2016/01/29 00:41:03]

Done.

+  static ZygoteHandle zygote = CreateZygote();
+  return zygote;
+}
+
 }  // namespace content