This is expected; we haven't implemented the feature for Android yet - moving Unconfirmed->Untriaged. :)

I am trying to implement this feature. See https://codereview.chromium.org/1140113002/.
Welcome to give comments and suggestions.

OK, cool. :) Note that screen-capture via getUserMedia() is not yet
standardized, and the desktop Chrome support is currently behind a
whitelist, so it's not a feature available to general web content as yet.

Desktop Chrome support is ACLed to extensions, not to a whitelist.

Hi, all. I write a short design doc https://docs.google.com/document/d/13-OKb_MyTwYlCULEeRxtDD_N8TqBhHaOWC6ZIYOrC7s/edit?usp=sharing to describe my implementation. There lists the security issue and some design concerns. I am eager to get more valuable opinions and push this work continue.

Currently, I am considering to adopt @sergey's advice to hide the feature behind a compile-time flag, disabled by default. I want to know if this method is acceptable and is there any other problem we need to resolve? Thanks.

I'll take it from here.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2f731e17983201082d9fc725cf7717868fc1e75d

commit 2f731e17983201082d9fc725cf7717868fc1e75d
Author: braveyao <braveyao@chromium.org>
Date: Fri Jul 01 22:36:08 2016

ScreenCapture for Android phase1, part I

The document about ScreenCapture for Android is here, https://goo.gl/QNH29g.
This cl is mainly based on the https://codereview.chromium.org/1140113002/.
Only the codes under media/ are included here, which implements the JAVA
capture with Android MediaProjection API and JNI connectors, with some issues
fixed so it can always work.
The control part in content/ and chrome/ will be in the next cl, as part II.

BUG=487935

Review-Url: https://codereview.chromium.org/1917023003
Cr-Commit-Position: refs/heads/master@{#403555}

[modify] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/chrome/android/BUILD.gn
[modify] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/content/app/android/library_loader_hooks.cc
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/content/browser/media/capture/screen_capture_device_android.cc
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/content/browser/media/capture/screen_capture_device_android.h
[modify] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/content/content_browser.gypi
[modify] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/content/public/android/BUILD.gn
[modify] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/BUILD.gn
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/BUILD.gn
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/java/src/org/chromium/media/ScreenCapture.java
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/screen_capture_jni_registrar.cc
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/screen_capture_jni_registrar.h
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/screen_capture_machine_android.cc
[add] https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d/media/capture/content/android/screen_capture_machine_android.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f9fdeda904daa23f306c6adc9f629756db3beeed

commit f9fdeda904daa23f306c6adc9f629756db3beeed
Author: kelvinp <kelvinp@chromium.org>
Date: Fri Jul 01 22:59:17 2016

Revert of ScreenCapture for Android phase1, part I (patchset #12 id:340001 of https://codereview.chromium.org/1917023003/ )

Reason for revert:
Break compile step on Android

Builder logs:
https://build.chromium.org/p/chromium/builders/Android/builds/58512/steps/compile/logs/stdio

Failure:
In file included from ../../media/capture/content/thread_safe_capture_oracle.h:15:0,
                 from ../../media/capture/content/screen_capture_device_core.h:15,
                 from ../../media/capture/content/android/screen_capture_machine_android.h:12,
                 from ../../media/capture/content/android/screen_capture_jni_registrar.cc:10:
../../media/capture/video/video_capture_device.h:33:55: fatal error: media/mojo/interfaces/image_capture.mojom.h: No such file or directory
 #include "media/mojo/interfaces/image_capture.mojom.h"

Original issue's description:
> ScreenCapture for Android phase1, part I
>
> The document about ScreenCapture for Android is here, https://goo.gl/QNH29g.
> This cl is mainly based on the https://codereview.chromium.org/1140113002/.
> Only the codes under media/ are included here, which implements the JAVA
> capture with Android MediaProjection API and JNI connectors, with some issues
> fixed so it can always work.
> The control part in content/ and chrome/ will be in the next cl, as part II.
>
> BUG=487935
>
> Committed: https://crrev.com/2f731e17983201082d9fc725cf7717868fc1e75d
> Cr-Commit-Position: refs/heads/master@{#403555}

TBR=dalecurtis@chromium.org,mcasas@chromium.org,michaelbai@chromium.org,miu@chromium.org,qinmin@chromium.org,sergeyu@chromium.org,tedchoc@chromium.org,braveyao@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=487935

Review-Url: https://codereview.chromium.org/2116883002
Cr-Commit-Position: refs/heads/master@{#403557}

[modify] https://crrev.com/f9fdeda904daa23f306c6adc9f629756db3beeed/chrome/android/BUILD.gn
[modify] https://crrev.com/f9fdeda904daa23f306c6adc9f629756db3beeed/content/app/android/library_loader_hooks.cc
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/content/browser/media/capture/screen_capture_device_android.cc
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/content/browser/media/capture/screen_capture_device_android.h
[modify] https://crrev.com/f9fdeda904daa23f306c6adc9f629756db3beeed/content/content_browser.gypi
[modify] https://crrev.com/f9fdeda904daa23f306c6adc9f629756db3beeed/content/public/android/BUILD.gn
[modify] https://crrev.com/f9fdeda904daa23f306c6adc9f629756db3beeed/media/capture/BUILD.gn
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/BUILD.gn
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/java/src/org/chromium/media/ScreenCapture.java
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/screen_capture_jni_registrar.cc
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/screen_capture_jni_registrar.h
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/screen_capture_machine_android.cc
[delete] https://crrev.com/b763ce88f69183ca5ffde59cc41ca047e5db6b7f/media/capture/content/android/screen_capture_machine_android.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7508a100080e04e8c430777aab7cb91cbcdd1ced

commit 7508a100080e04e8c430777aab7cb91cbcdd1ced
Author: braveyao <braveyao@chromium.org>
Date: Thu Jul 07 00:06:17 2016

Reland: ScreenCapture for Android phase1, part I
(patchset #12 id:340001 https://codereview.chromium.org/1917023003/)

Which got reverted due to breakage of compiling on Android bots intermittently.
(see https://codereview.chromium.org/2116883002)
Recenctly, media/capture/video/video_capture_device.h starts to include
media/mojo/interfaces/image_capture.mojom.h, which also requests the dependency
to //media/mojo/interfaces:image_capture. So does same thing to
media/capture/content/android/BUILD.gn. No other changed involved.

Original description --------------------------------------
ScreenCapture for Android phase1, part I

The document about ScreenCapture for Android is here, https://goo.gl/QNH29g.
This cl is mainly based on the https://codereview.chromium.org/1140113002/.
Only the codes under media/ are included here, which implements the JAVA
capture with Android MediaProjection API and JNI connectors, with some issues
fixed so it can always work.
The control part in content/ and chrome/ will be in the next cl, as part II.

BUG=487935
-----------------------------------------------------------------------
BUG = 487935

TBR=dalecurtis@chromium.org,mcasas@chromium.org,michaelbai@chromium.org,miu@chromium.org,qinmin@chromium.org,tedchoc@chromium.org

Review-Url: https://codereview.chromium.org/2125973002
Cr-Commit-Position: refs/heads/master@{#403996}

[modify] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/chrome/android/BUILD.gn
[modify] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/content/app/android/library_loader_hooks.cc
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/content/browser/media/capture/screen_capture_device_android.cc
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/content/browser/media/capture/screen_capture_device_android.h
[modify] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/content/content_browser.gypi
[modify] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/content/public/android/BUILD.gn
[modify] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/BUILD.gn
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/BUILD.gn
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/java/src/org/chromium/media/ScreenCapture.java
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/screen_capture_jni_registrar.cc
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/screen_capture_jni_registrar.h
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/screen_capture_machine_android.cc
[add] https://crrev.com/7508a100080e04e8c430777aab7cb91cbcdd1ced/media/capture/content/android/screen_capture_machine_android.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/92b46bda640a3bd8f1639778309458e852d84df6

commit 92b46bda640a3bd8f1639778309458e852d84df6
Author: braveyao <braveyao@chromium.org>
Date: Tue Aug 09 18:07:25 2016

Android: add screen share icon for permission infobar

This is to add new screen share icon for the upcoming screen capture feature
in chrome on Android(in cl https://codereview.chromium.org/2123863004/).
The permission infobar with this screen share icon will be promoted each time
when screen sharing is requested.

BUG=487935

Review-Url: https://codereview.chromium.org/2226123002
Cr-Commit-Position: refs/heads/master@{#410741}

[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/android/java/res/drawable-hdpi/infobar_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/android/java/res/drawable-mdpi/infobar_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/android/java/res/drawable-xhdpi/infobar_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/android/java/res/drawable-xxhdpi/infobar_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/android/java/res/drawable-xxxhdpi/infobar_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/app/theme/default_100_percent/common/infobar_media_stream_screen_share.png
[add] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/app/theme/default_200_percent/common/infobar_media_stream_screen_share.png
[modify] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/app/theme/theme_resources.grd
[modify] https://crrev.com/92b46bda640a3bd8f1639778309458e852d84df6/chrome/browser/android/resource_id.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94

commit dbb85e451ee0ffe9d18300befb9c0d0664b5ee94
Author: braveyao <braveyao@chromium.org>
Date: Fri Sep 23 18:49:08 2016

ScreenCapture for Android phase1, part II

The capture part has been landed in cl https://codereview.chromium.org/2125973002/.
This cl is to implement the control part in chrome/ and content/. The document
is here, https://goo.gl/QNH29g.
This cl proposes a pemission design on Android, including permission info bar
and head up notification, which will show up each time at starting screen capture
and user can check/stop the capture without leaving current page.
And all of these is behind a flag as an experimental feature.

BUG=487935

Review-Url: https://codereview.chromium.org/2123863004
Cr-Commit-Position: refs/heads/master@{#420679}

[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/java/src/org/chromium/chrome/browser/media/MediaCaptureNotificationService.java
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/java/src/org/chromium/chrome/browser/tab/TabWebContentsDelegateAndroid.java
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/java/src/org/chromium/chrome/browser/tab/TabWebContentsObserver.java
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabWindowManager.java
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/java/strings/android_chrome_strings.grd
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/android/javatests/src/org/chromium/chrome/browser/tabmodel/TabWindowManagerTest.java
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/app/generated_resources.grd
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/BUILD.gn
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/about_flags.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/android/chrome_feature_list.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/android/chrome_feature_list.h
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/android/tab_web_contents_delegate_android.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/media_stream_capture_indicator.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/media_stream_capture_indicator.h
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/media_stream_devices_controller_browsertest.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/permission_bubble_media_access_handler.cc
[add] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/screen_capture_infobar_delegate_android.cc
[add] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/chrome/browser/media/webrtc/screen_capture_infobar_delegate_android.h
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/components/infobars/core/infobar_delegate.h
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/content/browser/BUILD.gn
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/content/browser/renderer_host/media/video_capture_manager.cc
[modify] https://crrev.com/dbb85e451ee0ffe9d18300befb9c0d0664b5ee94/tools/metrics/histograms/histograms.xml

Now screen capture is available with some basic functionalities on Android behind a flag. 

How to test it:
- in chrome://flags page, enable the flag "Experimental ScreenCapture android"
- getUserMedia with constraints "video: {'mandatory': {'chromeMediaSource':'screen'}}". And you can specify frame size and frame rate as well. (Audio must be set to false.)
- click Allow on the permission infobar.
- When you firstly request screen capture, there is also a system permission dialog (which is supposed to be shown each time at requesting screen capture). At present, it's best to check the option "Don't show again" and click "START NOW". Then it won't emerge next time.
- screen capture should start to work. There is a notification to suggest on going screen capture and you can also stop capture there without leaving the page.

What's coming soon:
- Device rotation support. Currently rotating the device will cause the black padding.
- Show notification after screen capture starts. Currently they are shown at same time. The head-up notification may cause some delayed response of clicking the "START NOW' button in the system permission dialog.

Known issues(we are asking support from Android side, so they may be solved in the future):
- Dual permission. At present there will be both permission infobar from Chrome and permission dialog from system(if you didn't choose "Dont show again") to start screen capture. 
- We prefer I420 output of MediaProjection. But it's only available on some devices and we'll fallback to RGBA_8888 if the device reports failure to I420 request. But some device may fail silently and no screen capture available.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a2f67c812a83157e7eb24b81fd3aa51e978fbfb8

commit a2f67c812a83157e7eb24b81fd3aa51e978fbfb8
Author: mostynb <mostynb@opera.com>
Date: Sat Sep 24 06:53:50 2016

unbreak builds with webrtc disabled

https://codereview.chromium.org/2123863004 broke non-webrtc non-android
builds.  Let's fix that.

BUG=487935

Review-Url: https://codereview.chromium.org/2370583002
Cr-Commit-Position: refs/heads/master@{#420832}

[modify] https://crrev.com/a2f67c812a83157e7eb24b81fd3aa51e978fbfb8/content/browser/renderer_host/media/video_capture_manager.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/709ed4c443cb400660e0d88c888a0e9a4fbd5536

commit 709ed4c443cb400660e0d88c888a0e9a4fbd5536
Author: braveyao <braveyao@chromium.org>
Date: Sat Nov 05 01:12:06 2016

Android ScreenCapture: add support to device rotation.

When device is rotated during screen capturing with MediaProjection API
on Android, the rotated screen will be captured and fit into the frame requested
with padding. So when we detect a device rotation, we need to re-create capture
with the new orientation and update the oracle.

Also refactored(mainly reordered some lines) the java file a bit for a newly
added unittest file.

BUG=487935

Review-Url: https://codereview.chromium.org/2468383002
Cr-Commit-Position: refs/heads/master@{#430111}

[modify] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/content/browser/media/capture/screen_capture_device_android.h
[add] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/content/browser/media/capture/screen_capture_device_android_unittest.cc
[modify] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/content/test/BUILD.gn
[modify] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/media/capture/content/android/java/src/org/chromium/media/ScreenCapture.java
[modify] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/media/capture/content/android/screen_capture_machine_android.cc
[modify] https://crrev.com/709ed4c443cb400660e0d88c888a0e9a4fbd5536/media/capture/content/android/screen_capture_machine_android.h

Bumping to M57. Please update if that's wrong.

Hi, 

   I did a test with revision M-55. Works! But when I leaved Chrome (change to another application), the streaming stoped (freeze)! Is it normal?

Tks a lot.

That depends. 
When you switch back to Chrome, will the capture continue? Or chrome will be re-launched totally? There are some Apps are too huge and Android will terminate the background apps. Please double check if this is your case.

Yes, when I back to Chrome the capture continue. I Made an example: https://drive.google.com/file/d/0B3DQ5vCWbTeDdjhnR2MwSzZoQ0U/view

Android 6.0.1;SM-A510M Build/MMB29K - Chrome 55.0.2883.91

Thanks for the report! It's a regression, in which I gave a wrong review comments. Trying to land a fix soon.

Bumping this to M58. Please correct if that's wrong.