Enable backend switching for Windows Viewer

Enable backend switching for Windows Viewer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2184163003

Committed: https://skia.googlesource.com/skia/+/b8794ccea2163c780760b6e0f7ebd022f2c85d33

[jvanverth1, 2016-07-27 20:06:51]

Description was changed from

==========
Enable backend switching for Windows Viewer

BUG=skia:
==========

to

==========
Enable backend switching for Windows Viewer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2184163003
==========

[jvanverth1, 2016-07-27 20:10:46]

jvanverth@google.com changed reviewers:
+ bsalomon@google.com

[bsalomon, 2016-07-27 20:26:38]

lgtm w/ question about whether we need to get the dc.

https://codereview.chromium.org/2184163003/diff/1/tools/viewer/sk_app/win/GLW...
File tools/viewer/sk_app/win/GLWindowContext_win.cpp (right):

https://codereview.chromium.org/2184163003/diff/1/tools/viewer/sk_app/win/GLW...
tools/viewer/sk_app/win/GLWindowContext_win.cpp:99: HDC dc = GetDC(fHWND);
Should this be paired with a ReleaseDC? Or do we really need to have a
wglMakeCurrent before wglDeleteContext?

From the docs it sounds like it just can't be current on another thread. If it's
current on the calling thread then it becomes not-current in wglDeleteContext.

[jvanverth1, 2016-07-27 20:41:50]

https://codereview.chromium.org/2184163003/diff/1/tools/viewer/sk_app/win/GLW...
File tools/viewer/sk_app/win/GLWindowContext_win.cpp (right):

https://codereview.chromium.org/2184163003/diff/1/tools/viewer/sk_app/win/GLW...
tools/viewer/sk_app/win/GLWindowContext_win.cpp:99: HDC dc = GetDC(fHWND);
Deleted. I added this in to try and figure out why OpenGL wouldn't shut down
enough to let Vulkan create a swapchain. It doesn't need to be there now.

[jvanverth1, 2016-07-27 20:42:13]

The CQ bit was checked by jvanverth@google.com

[jvanverth1, 2016-07-27 20:42:14]

The patchset sent to the CQ was uploaded after l-g-t-m from bsalomon@google.com
Link to the patchset: https://codereview.chromium.org/2184163003/#ps20001
(title: "Delete extra glMakeCurrent")

[commit-bot: I haz the power, 2016-07-27 20:42:23]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-27 21:29:20]

Description was changed from

==========
Enable backend switching for Windows Viewer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2184163003
==========

to

==========
Enable backend switching for Windows Viewer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2184163003

Committed:
https://skia.googlesource.com/skia/+/b8794ccea2163c780760b6e0f7ebd022f2c85d33
==========

[commit-bot: I haz the power, 2016-07-27 21:29:23]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/b8794ccea2163c780760b6e0f7ebd022f2c85d33