Use RecvMsgWithPid to find real PID for zygote children

content/public/common/child_process_sandbox_support_linux.h

Index: content/public/common/child_process_sandbox_support_linux.h
diff --git a/content/public/common/child_process_sandbox_support_linux.h b/content/public/common/child_process_sandbox_support_linux.h
index 9e1cde273ad35201ff0353fec356ca8bf134b9dd..58dc3ea8bf54de77044b8dce2e97f4b51205abca 100644
--- a/content/public/common/child_process_sandbox_support_linux.h
+++ b/content/public/common/child_process_sandbox_support_linux.h
@@ -50,6 +50,10 @@ CONTENT_EXPORT int MatchFontWithFallback(
 CONTENT_EXPORT bool GetFontTable(int fd, uint32_t table_tag, off_t offset,
                                  uint8_t* output, size_t* output_length);
 
+// Sends a zygote child "ping" message to browser process via socket |fd|.
+// Returns true on success.
+CONTENT_EXPORT bool SendZygoteChildPing(int fd);
+
 };  // namespace content
 
 #endif  // CONTENT_PUBLIC_COMMON_CHILD_PROCESS_SANDBOX_SUPPORT_LINUX_H_