I am interested to work on this.
Plz let me know

You're most welcome to! Thanks.

I'm assigning this to myself as I can't assign to you, but it's all yours :).

dominickn was also really keen to work on this.

Submitted below patch. PTAL
https://chromium-review.googlesource.com/c/chromium/src/+/758456

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/761e67a03549d289401b4a98409d2d8391a66dbb

commit 761e67a03549d289401b4a98409d2d8391a66dbb
Author: cm.sanchi <cm.sanchi@samsung.com>
Date: Thu Nov 16 08:23:28 2017

Permissions: Remove CONTENT_SETTINGS_TYPE_PUSH_MESSAGING

CONTENT_SETTINGS_TYPE_PUSH_MESSAGING is exactly equivalent with
CONTENT_SETTINGS_TYPE_NOTIFICATIONS now. This patch removes
all its references

Bug:  781672 
Change-Id: I81f6f0938d75a30db97c140f3232784931b6d027
Reviewed-on: https://chromium-review.googlesource.com/758456
Commit-Queue: srirama chandra sekhar <srirama.m@samsung.com>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517027}
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/android_webview/browser/aw_permission_manager.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/notifications/notification_permission_context.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/notifications/notification_permission_context.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/notifications/notification_permission_context_unittest.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_context_base.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_context_base.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_context_base_feature_policy_unittest.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_context_base_unittest.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_decision_auto_blocker.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_manager.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_manager_unittest.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_request.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_request_impl.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_request_manager_browsertest.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_uma_util.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_util.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/permissions/permission_util.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/push_messaging/push_messaging_service_impl.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/safe_browsing/permission_reporter.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/chrome/browser/ui/webui/site_settings_helper.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/components/content_settings/core/common/content_settings_types.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/browser/permissions/permission_service_impl.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/browser/push_messaging/push_messaging_manager.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/public/browser/permission_type.h
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/shell/browser/layout_test/layout_test_message_filter.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/shell/browser/layout_test/layout_test_permission_manager.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/content/shell/browser/layout_test/layout_test_push_messaging_service.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/headless/lib/browser/headless_permission_manager.cc
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/third_party/WebKit/Source/modules/permissions/Permissions.cpp
[modify] https://crrev.com/761e67a03549d289401b4a98409d2d8391a66dbb/third_party/WebKit/public/platform/modules/permissions/permission.mojom