Any plan to pursue the implementation of this feature in the near future? May I know why this implementation is no longer pursued? And, is there a way I could help?

I think this feature could enable developers to more easily build interesting pieces of software especially in the field of accessibility. Think of real-time and automatic closed-captioning of live video conferencing. It could be a life changer for the Deaf and Hard-of-Hearing. That's only one of the many applications it could have.

I started working on this without knowing about the bug. A CL is in progress.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5f93cebdc920d48612d7ec612c7c7724d715d7af

commit 5f93cebdc920d48612d7ec612c7c7724d715d7af
Author: Max Morin <maxmorin@chromium.org>
Date: Mon Nov 06 18:51:49 2017

Remove dead class SpeechRecognitionAudioSink.

It is only ever created when receiving a certain IPC message, which is never sent form the browser.
Also removed that IPC message and some supporting blink code

Bug:  701229 
Change-Id: I5be6957a411f2527b8f109161d887a6d200f2afd
Reviewed-on: https://chromium-review.googlesource.com/749181
Commit-Queue: Max Morin <maxmorin@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514196}
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/content/common/speech_recognition_messages.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/content/renderer/BUILD.gn
[delete] https://crrev.com/b995530b1d8cebcba74e7db87a6837cfd5e219c4/content/renderer/media/speech_recognition_audio_sink.cc
[delete] https://crrev.com/b995530b1d8cebcba74e7db87a6837cfd5e219c4/content/renderer/media/speech_recognition_audio_sink.h
[delete] https://crrev.com/b995530b1d8cebcba74e7db87a6837cfd5e219c4/content/renderer/media/speech_recognition_audio_sink_unittest.cc
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/content/renderer/speech_recognition_dispatcher.cc
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/content/renderer/speech_recognition_dispatcher.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/content/test/BUILD.gn
[delete] https://crrev.com/b995530b1d8cebcba74e7db87a6837cfd5e219c4/third_party/WebKit/LayoutTests/fast/speech/scripted/speechrecognition-audiotrack.html
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognition.cpp
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognition.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognition.idl
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognitionClient.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognitionClientProxy.cpp
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognitionClientProxy.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/modules/speech/SpeechRecognitionController.h
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/Source/platform/runtime_enabled_features.json5
[modify] https://crrev.com/5f93cebdc920d48612d7ec612c7c7724d715d7af/third_party/WebKit/public/web/WebSpeechRecognitionParams.h