gpu/linux: create a child window to control resize and avoid flashes

gpu/linux: create a child window to control resize and avoid flashes

When the window is resized, some drivers clobber the back buffer.
Unfortunately that can happen in the middle of a frame, and so we lose part
of what we've drawn and don't know it until we swapped (resulting in
flashes).

So instead, we create a child window, with a CopyFromParent visual (to avoid
inducing extra blits in the driver), that we can resize exactly in Resize(),
correctly ordered with GL, so that the buffer clobber is at the beginning of the
frame, before we will draw anything to it.

BUG=326995
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272290

[danakj, 2014-05-22 16:08:20]

Super clever!

[ccameron, 2014-05-22 16:14:05]

On 2014/05/22 16:08:20, danakj wrote:
> Super clever!

Huh - wow. LGTM

[piman, 2014-05-22 16:41:57]

The CQ bit was checked by piman@chromium.org

[commit-bot: I haz the power, 2014-05-22 16:42:50]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/piman@chromium.org/296003010/1

[commit-bot: I haz the power, 2014-05-22 19:58:27]

Change committed as 272290

[ccameron, 2014-05-23 09:09:05]

https://codereview.chromium.org/296003010/diff/1/ui/gl/gl_surface_glx.cc
File ui/gl/gl_surface_glx.cc (right):

https://codereview.chromium.org/296003010/diff/1/ui/gl/gl_surface_glx.cc#newc...
ui/gl/gl_surface_glx.cc:426: XMapWindow(g_display, window_);
Looking back at
https://chromiumcodereview.appspot.com/23452026/diff/51001/ui/gl/gl_surface_g...,
it looks like I had to do an XFlush here (after the XMapWindow) ... I didn't
write why I had it there, so I can't say if it is indeed necessary.