takumif@ is the plan still to only add it after the views-based UI gets landed? If so, can you marked this as blocked?

This should be fairly easy to add but the trusted area does not support animations for having it fade in when added or similar. I think that's fine.

The implementations don't depend on each other so I'm not sure if we should mark this as blocked by issue 754101, but yes I think it makes sense to put the changes behind the same flag (#views-cast-dialog) and launch at the same time.

Takumi, looks like you're going to add this for when the Harmony UX ships correct?

Right, and I'd like pbos@ to help with the implementation.

Is this looking like M70 now?

Right, we're no longer targeting M69.

Cool. As a DAILY cast user, I am still looking forward to this :)

I wrote a quick design doc:
https://docs.google.com/document/d/1gRWSUj5S0XAAG2L3CRAu6-g4BdejErIg703zTbgoQGE/edit#

Peter, are you available to work on this for M70?

I think I'll be able to consult, but I can't promise much more. I'm also off for 4 weeks starting Aug 20, so that might sort of interfere.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a70cc1ce37074cfc9981b088ced363253b9f3c37

commit a70cc1ce37074cfc9981b088ced363253b9f3c37
Author: Takumi Fujimoto <takumif@chromium.org>
Date: Fri Aug 17 21:48:01 2018

Put the Cast toolbar icon in the trusted area behind a flag

The Cast toolbar icon has been in the same section as extension icons.
This CL puts the icon in the trusted area of the toolbar if the
ViewsCastDialog flag is enabled. CastToolbarButton, the main icon object,
is owned by ToolbarView, just like AvatarToolbarButton.

CastToolbarButton observes MediaRouterActionController (to be renamed in
a later patch, because "Action" is specific to the old icon) and sets its
visibility and pressed state accordingly.

When the ViewsCastDialog flag is disabled, the old icon is used.

Screencap: https://drive.google.com/open?id=1IMxDzKSiR8AJ89muOy1-_NDLp0RNYAau

Bug:  859216 
Change-Id: I0ec14e6d20dd58b0356166520c8511e3f9027b83
Reviewed-on: https://chromium-review.googlesource.com/1158794
Reviewed-by: Peter Boström <pbos@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584205}
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/toolbar/media_router_action_controller.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/toolbar/media_router_action_controller.h
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/toolbar/media_router_contextual_menu.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/toolbar/media_router_contextual_menu.h
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/toolbar/media_router_contextual_menu_unittest.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/cast_dialog_view.cc
[add] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/cast_toolbar_button.cc
[add] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/cast_toolbar_button.h
[add] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/cast_toolbar_button_unittest.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/cloud_services_dialog_view.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/media_remoting_dialog_view.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/media_router_dialog_controller_views.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/media_router/media_router_ui_browsertest.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/toolbar/toolbar_button.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/toolbar/toolbar_button.h
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/toolbar/toolbar_view.cc
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/browser/ui/views/toolbar/toolbar_view.h
[modify] https://crrev.com/a70cc1ce37074cfc9981b088ced363253b9f3c37/chrome/test/BUILD.gn

r584205 seems to crash Canary during startup, stacktrace attached - is it something obvious or should I file a new issue?

Can you please report the platform/version you're seeing this happen on?  Chrome Canary starts fine for me on Mac (70.0.3528.0).

Thanks for the report. I'm seeing crash reports with the same stack trace at issue 875868 (you may not be able to access it). I'll look into it.

The crash should repro only when the views-cast-dialog feature in chrome://flags (or --enable-features=ViewsCastDialog) is enabled, either manually or by an experiment.

The crash should now be fixed by crrev.com/c/1181934.