Reland 28629004: adding new AEC dump start interface for chrome.

This is required because we are not allow to pass CRT objects across dll boundaries, that says, when we pass a file descriptor from chrome dll to libpeerconnection dll, the file descriptor will become invalid immediate, more information can be found here:
http://msdn.microsoft.com/en-us/library/ms235460.aspx

R=andresp@webrtc.org, andrew@webrtc.org, bjornv@webrtc.org, henrike@webrtc.org, henrikg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/30629004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7418 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index 3be8a3a..be53e40 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -111,6 +111,8 @@
     "md5.cc",
     "md5.h",
     "md5digest.h",
+    "platform_file.cc",
+    "platform_file.h",
     "stringencode.cc",
     "stringencode.h",
     "stringutils.cc",