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

chromecast/browser/cast_content_browser_client.cc

Index: chromecast/browser/cast_content_browser_client.cc
diff --git a/chromecast/browser/cast_content_browser_client.cc b/chromecast/browser/cast_content_browser_client.cc
index ebce67d15f4549b440b5da0d8e30934bf194375f..c5cd5b46ef4b03b81bd5dc6fd28d8404667dcfd3 100644
--- a/chromecast/browser/cast_content_browser_client.cc
+++ b/chromecast/browser/cast_content_browser_client.cc
@@ -134,6 +134,13 @@ void CastContentBrowserClient::AppendExtraCommandLineSwitches(
   base::CommandLine* browser_command_line =
       base::CommandLine::ForCurrentProcess();
 
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  if (process_type != switches::kZygoteProcess) {
+    command_line->AppendSwitch(::switches::kV8NativesPassedByFD);
+    command_line->AppendSwitch(::switches::kV8SnapshotPassedByFD);
+  }
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+
   // IsCrashReporterEnabled() is set when InitCrashReporter() is called, and
   // controlled by GetBreakpadClient()->EnableBreakpadForProcess(), therefore
   // it's ok to add switch to every process here.