Expose UpdateOffscreenFrameBufferSize from GLES2Decoder to allow Mac...

Expose UpdateOffscreenFrameBufferSize from GLES2Decoder to allow Mac
port to call it during resizing. Because the Mac port does all of its
rendering offscreen, the back buffer must be resized immediately
rather than waiting until the next SwapBuffers call.

Tested with npapi_pepper_test_plugin and GPU unit tests.

BUG=45246
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=48789

[Ken Russell (switch to Gerrit), 2010-06-02 17:29:51]

Please review. Thanks.

[greggman, 2010-06-02 17:34:33]

LGTM from me but I think Al should really be the one to ok this.

[apatrick, 2010-06-02 17:35:03]

http://codereview.chromium.org/2466003/diff/1/4
File gpu/command_buffer/service/gpu_processor_mac.cc (right):

http://codereview.chromium.org/2466003/diff/1/4#newcode74
gpu/command_buffer/service/gpu_processor_mac.cc:74:
decoder_->UpdateOffscreenFrameBufferSize();
Don't these get called as a result of asynchronous messages from the renderer or
browser process? If that is the case, what prevents a partial frame worth of
OpenGL calls from rendering into a newly resized offscreen frame buffer?

[Ken Russell (switch to Gerrit), 2010-06-02 17:47:37]

http://codereview.chromium.org/2466003/diff/1/4
File gpu/command_buffer/service/gpu_processor_mac.cc (right):

http://codereview.chromium.org/2466003/diff/1/4#newcode74
gpu/command_buffer/service/gpu_processor_mac.cc:74:
decoder_->UpdateOffscreenFrameBufferSize();
On 2010/06/02 17:35:04, apatrick wrote:
> Don't these get called as a result of asynchronous messages from the renderer
or
> browser process? If that is the case, what prevents a partial frame worth of
> OpenGL calls from rendering into a newly resized offscreen frame buffer?

In Pepper 3D, an asynchronous resize message from the browser triggers the
application's repaint callback, so the app will redraw from scratch in response
to it. On the Mac the resizing of the back buffer must occur immediately, or
there is no valid back buffer for the app to draw into. It is possible there are
issues on other platforms as well. I suspect we will encounter them when turning
on compositing of Pepper 3D plugins. We need more tests of this functionality,
in particular examples which do live resizing.

[apatrick_chromium, 2010-06-02 19:49:02]

LGTM