Use GL_LINEAR for backing texture of offscreen framebuffer.

Use GL_LINEAR for backing texture of offscreen framebuffer.

The texture filtering mode of backing texture of offscreen
framebuffer is used for rendering Pepper Graphics3D contents.
If GL_NEAREST is used, the contents looks bad when it is scaled
(e.g. CSS transform, changing display resolution on ChromeOS).
This CL changes the texture filtering mode of backing textures
to GL_LINEAR to prevent the contents from looking bad in such cases.

TEST=Set display resolution to 1024x680 on Pixel
TEST=Apply CSS transform to NaCl emebed element
TEST=Apply CSS transform to Flash content
BUG=384687
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290116

[mazda, 2014-08-13 12:55:22]

Hi piman,

Could you review this change?

Another option I thought about was to use GL_LINEAR for the texture shared via
texture mailbox in compositor side regardless of the original filtering mode,
but I didn't adopt because it might be confusing.
Please let me know if there are any better fixes.

Thanks,

[piman, 2014-08-15 17:58:29]

LGTM. The compositor assumes (at first) the texture it's given is GL_LINEAR. It
may change the filtering, e.g. disabling filtering if pixel-aligned with no
scaling.
The code you're changing is only used for pepper, which only gives it to the
compositor, so it's reasonable to change it to be GL_LINEAR to match what the
compositor expects.

[mazda, 2014-08-16 03:28:21]

The CQ bit was checked by mazda@chromium.org

[commit-bot: I haz the power, 2014-08-16 03:29:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mazda@chromium.org/472443002/1

[commit-bot: I haz the power, 2014-08-16 04:50:39]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  mac_chromium_compile_dbg on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[commit-bot: I haz the power, 2014-08-16 07:46:31]

Committed patchset #1 (1) as 290116