Implement writing mic audio input data to file for debugging purposes.

content/renderer/media/aec_dump_message_filter.cc

Index: content/renderer/media/aec_dump_message_filter.cc
diff --git a/content/renderer/media/aec_dump_message_filter.cc b/content/renderer/media/aec_dump_message_filter.cc
index 3788e18df30eb3226aacbf3732e199088afba505..76f104ca4592496237b0a7d7a2009f39eaee35f8 100644
--- a/content/renderer/media/aec_dump_message_filter.cc
+++ b/content/renderer/media/aec_dump_message_filter.cc
@@ -22,7 +22,7 @@ AecDumpMessageFilter::AecDumpMessageFilter(
     const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner)
     : sender_(NULL),
-      delegate_id_counter_(0),
+      delegate_id_counter_(1),
       io_task_runner_(io_task_runner),
       main_task_runner_(main_task_runner) {
   DCHECK(!g_filter);