initialize trace_event hooks in angle on gpu startup

initialize trace_event hooks in angle on gpu startup

Requires https://codereview.appspot.com/12699047/

R=apatrick@chromium.org
BUG=270179
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=217487

[apatrick_chromium, 2013-08-12 19:34:12]

https://codereview.chromium.org/22744005/diff/1/content/gpu/gpu_main.cc
File content/gpu/gpu_main.cc (right):

https://codereview.chromium.org/22744005/diff/1/content/gpu/gpu_main.cc#newco...
content/gpu/gpu_main.cc:116:
gl::SetTraceFunctionPointers(&AngleGetTraceCategoryEnabledFlag,
Does this really work? ANGLE is dynamically loaded. Also what if we're using
OpenGL or Mesa instead of ANGLE? Also, what about platforms other than Windows?

[scottmg, 2013-08-12 20:13:26]

On 2013/08/12 19:34:12, apatrick_chromium wrote:
> https://codereview.chromium.org/22744005/diff/1/content/gpu/gpu_main.cc
> File content/gpu/gpu_main.cc (right):
> 
>
https://codereview.chromium.org/22744005/diff/1/content/gpu/gpu_main.cc#newco...
> content/gpu/gpu_main.cc:116:
> gl::SetTraceFunctionPointers(&AngleGetTraceCategoryEnabledFlag,
> Does this really work? ANGLE is dynamically loaded. Also what if we're using
> OpenGL or Mesa instead of ANGLE? Also, what about platforms other than
Windows?

It does work locally (in that I get trace data for ANGLE when I do this).

Are you sure it's dynamically loaded? It looks like various places have a
dependency on libGLESv2
https://code.google.com/p/chromium/codesearch#search/&q=libglesv2%20file:.gyp...

and it's just a shared_library
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/angle_...
so I think it's being loaded as a regular DLL dependency?

(I admit it doesn't seem like a great thing... but I guess it's just setting
function pointers that are unused when in desktop or mesa)

Assuming we switched it to actually be dynamically loaded, any suggestions on
better ways to initialize these callbacks?

[apatrick_chromium, 2013-08-12 20:21:52]

It has to happen really early. You could try ui\gl\gl_implementation_win.cc in
InitializeGLBindings, being careful to only do it for ANGLE, e.g. implementation
is kGLImplementationEGLGLES2 and SwiftShader isn't active.

[scottmg, 2013-08-14 00:38:45]

moved to gl_implementation_win, use getprocaddress instead of __declspec so
there's no hard dep on libGLESv2.dll, included function prototype here so
there's no dependency on particular ANGLE rev.

[apatrick_chromium, 2013-08-14 00:42:48]

lgtm

[commit-bot: I haz the power, 2013-08-14 01:07:45]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/scottmg@chromium.org/22744005/15001

[commit-bot: I haz the power, 2013-08-14 05:47:01]

Change committed as 217487