Use command line to signal whether a child process was passed V8 snapshot files via file descriptor

content/shell/browser/shell_content_browser_client.cc

Index: content/shell/browser/shell_content_browser_client.cc
diff --git a/content/shell/browser/shell_content_browser_client.cc b/content/shell/browser/shell_content_browser_client.cc
index 07d114815364f37b1753121ed4a049c523b676a0..fc03843c0830ae4aa60860821fa40fd451bf1523 100644
--- a/content/shell/browser/shell_content_browser_client.cc
+++ b/content/shell/browser/shell_content_browser_client.cc
@@ -209,6 +209,16 @@ bool ShellContentBrowserClient::IsHandledURL(const GURL& url) {
 void ShellContentBrowserClient::AppendExtraCommandLineSwitches(
     base::CommandLine* command_line,
     int child_process_id) {
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  std::string process_type =
+      command_line->GetSwitchValueASCII(switches::kProcessType);
+  if (process_type != switches::kZygoteProcess) {
+    command_line->AppendSwitch(::switches::kV8NativesPassedByFD);
+    command_line->AppendSwitch(::switches::kV8SnapshotPassedByFD);
+  }
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+#endif  // OS_POSIX && !OS_MACOSX
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kRunLayoutTest))
     command_line->AppendSwitch(switches::kRunLayoutTest);