posted by wap, platform: Chrome
看图，就在新的开发者模式里面，估计要完善再放出来，和ART一样

posted by wap, platform: Chrome
Apparently Android M has included some multi-window support. This post will show you how to enable it, but it requires some knowledge of ADB and Linux shell commands.
Install and boot into TWRP recovery
Go into "Mount" and make sure "System" is mounted.
Connect your device to a computer with ADB. Make sure ADB is working using this command:
adb devices
We need to make some changes to build.prop. The following commands will allow us to edit this:
adb shell
cd /system
vi build.prop
To enable multi-window, we will need to change the line
ro.build.type=user
to
ro.build.type=userdebug
Exit the editor, and exit the shell, and hit reboot. You will get a warning about failing verification and how your device might not work properly, but as far as i know it's okay to just ignore that warning. At least, my Nexus 9 that I tried this on is still working just fine so far.
Go into developer options, and scroll down until you see "Multi-window mode". Enable that.
Go to recents, and hit the new icon that now shows up. Play around, and apps should now be able to run in split-screen. Beware, though, it's extremely buggy and not very usable at all.
To disable multi-window, just go into Developer Options and untoggle that setting. No need to edit build.prop again.

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reddit上提供的开启方法。