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

chrome/browser/chrome_content_browser_client.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chrome_content_browser_client.h"
 
 #include <set>
 #include <utility>
 #include <vector>
 
@@ skipping 1185 matching lines @@
   command_line->CopySwitchesFrom(browser_command_line, kChromeOSSwitches,
                                  arraysize(kChromeOSSwitches));
 
   // On Chrome OS need to pass primary user homedir (in multi-profiles session).
   base::FilePath homedir;
   PathService::Get(base::DIR_HOME, &homedir);
   command_line->AppendSwitchASCII(chromeos::switches::kHomedir,
                                   homedir.value().c_str());
 #endif
 
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+#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
+#endif  // OS_POSIX && !OS_MACOSX
+
   if (process_type == switches::kRendererProcess) {
     content::RenderProcessHost* process =
         content::RenderProcessHost::FromID(child_process_id);
     Profile* profile =
         process ? Profile::FromBrowserContext(process->GetBrowserContext())
                 : NULL;
     for (size_t i = 0; i < extra_parts_.size(); ++i) {
       extra_parts_[i]->AppendExtraRendererCommandLineSwitches(
           command_line, process, profile);
     }
@@ skipping 1190 matching lines @@
       switches::kDisableWebRtcEncryption,
     };
     to_command_line->CopySwitchesFrom(from_command_line,
                                       kWebRtcDevSwitchNames,
                                       arraysize(kWebRtcDevSwitchNames));
   }
 }
 #endif  // defined(ENABLE_WEBRTC)
 
 }  // namespace chrome