It will be only happened in ChromeOS

It is very difficult to take the photo via camera to expose the bug, below the mouse cursor, you can see some text which is belong to the brower window, not the wechat chrome app window

Deleted: 1806346691.jpg 38.7 KB

	1806346691.jpg 38.7 KB View Download

<triage>

Based on the description, seems the app is not totally opaque. I wonder if there a tool can quickly tell me the opacity under the cursor?

I can print out these parameters though to check.

I think it may be caused by the incorrect blending function or window compositor algorithm.

Because the browser content show in the dark part of a individual chrome window is not the top most page of browser sometimes.

You can make the chrome app secure shell as the test window, and make another browser window behind it.

What's more, it seems the text shown in dark part more obviously in the left part of the screen

Deleted: 989610913.jpg 2.5 MB

	989610913.jpg 2.5 MB View Download

I tested in desktop simulator and kevin on Chrome 59.0.3068.0, Platform 9439.0.0-17.04.07.
It looks fine to me. The black is opaque.

If you have a chance, could you turn on the flags --ash-debug-shortcuts, and press "CTRL + ALT + SHIFT" + L to print out the layer's info, including the opacity?

The info is in the log file: chrome. You can access it using the following commands:
open browser
CTRL + ALT + t
shell
cd
cd log
tail -f chrome

I will try device link tomorrow.
Could you be more specific what did you do in the second step:
2. Make the background or title bar be dark, either via HTML or chrome API

Thanks

I changed my device link into developer mode just now, bug logs shows opacity all OK.

chronos@localhost ~/log $ tail -f chrome | grep opacity
            opacity: 0
                  opacity: 0
                  opacity: 0
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
            opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
            opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
                  opacity: 0.00
            opacity: 0.00
               opacity: 0.00
      opacity: 0.00
            opacity: 0.00

I guess it may be the bug for graphics drivers now, not the chrome ... So it only happened in the screen rendering. And after some hours use, the bug appears more frequently and obviously, it looks like stable content displayed in the screen left some info will impact new content displayed in the same places. 

More easy steps to reproduce the bug:

1. open a web page, such as this page fullscreen
2. wait for at least 10 minutes, make the screen content stable
3. open secure shell, no login.
4. place the shell tab in the left part of the screen
5. you can see the effect like my photo uploaded before

Both my link and samus have the bug

The attached image is from device link, the title bar of wechat is grey than the black shell, but it is opaque.

Deleted: Screenshot 2017-04-11 at 9.43.55 AM.png 538 KB

	Screenshot 2017-04-11 at 9.43.55 AM.png 538 KB View Download

In the #12, the Chrome 58.0.2991.0, Platform 9197.0.0-17.01.18

the browser window content should be white background with dark color. the app window, or even the secure shell window should be dark.
and the bug appears in the left part of the screen.

in my link, even the files app (title bar part) has the bug. I think it is a graphics driver bug.

And only screen rendering has the bug, screenshot is always correct without any bugs.

Deleted: 1139016764.jpg 3.2 MB

	1139016764.jpg 3.2 MB View Download

Sorry I cannot reproduce this on LINK, Please see the attachment.
I changed my LINK version to Chrome: 57.0.2987.137/Platform: 9202.60.0

Deleted: Screenshot 2017-04-11 at 18.56.29.png 83.8 KB

	Screenshot 2017-04-11 at 18.56.29.png 83.8 KB View Download

On my screen, it looks good too.

Wait for a while, I do see the file app title can be see through.

Another thing is that if you put your browser on one position for a long time (until you can see through from the file app title), you move the browser to other place, and move the file app title back to the old position, you still can see the old text in the old position.

It might be the hardware issue with phantom images. 
see: https://support.apple.com/en-us/HT202580

+marcheu@, could you please verify this is a hardware issue and WontFix.

From the following links, it says that we use IPS display:
https://support.google.com/chromebook/answer/2762037
https://support.google.com/chromebook/answer/6164568

Yes this is burn-in on the panel, technically this is a hardware problem (the panel "remembers" the old colors when the same thing has been displayed for a while). This goes away once you start displaying something else.