Add OES_texture_half_float extension support in WebGL.

Add OES_texture_half_float extension support in WebGL.
It was firstly prototyped by Nayan Kumar K at
https://bugs.webkit.org/show_bug.cgi?id=110936.
This new patch refines the float to half-float conversion and adds
for support for more formats like RGB, ALPHA, LUMINANCE, and LUMINANCE_ALPHA.

BUG=233057

[Jun Jiang, 2013-04-22 09:23:06]

To make it work on Desktop GL Implementation, patch on
https://codereview.chromium.org/14402003/ is also needed. 

Tests have been done using
LayoutTests/fast/canvas/webgl/oes-texture-half-float.html and my test cases for
HTMLCanvas, Image, ImageData and HTMLVideo. These test cases will be either
upload to  https://github.com/KhronosGroup/WebGL.git or integrated into the
patch that enabling OES_texture_half_float test, such as
https://code.google.com/p/chromium/issues/detail?id=229197 or crbug.com/179503.

[Ken Russell (switch to Gerrit), 2013-04-24 02:21:14]

Jun, thanks for your work on this. It looks really good overall. One mechanical
change please.

https://codereview.chromium.org/13842017/diff/1/Source/core/platform/graphics...
File Source/core/platform/graphics/GraphicsContext3D.cpp (right):

https://codereview.chromium.org/13842017/diff/1/Source/core/platform/graphics...
Source/core/platform/graphics/GraphicsContext3D.cpp:269: unsigned short
convertFloatToHalfFloat(const float *f)
Please change this and the calling code to pass the incoming float by value. You
can still take the address of the incoming argument in order to reinterpret the
bits. This will eliminate the need for the temporary arrays in some of the
templates below.

[Ken Russell (switch to Gerrit), 2013-04-24 02:22:59]

Also, if it's possible for you to incorporate the newly integrated
oes-texture-half-float conformance tests (see
LayoutTests/webgl/generate-webgl-tests.py), that would be helpful. You'll need
to temporarily unskip the webgl/ tests in LayoutTests/TestExpectations in order
to make sure the new tests are working.

[Jun Jiang, 2013-04-24 15:57:16]

On 2013/04/24 02:22:59, kbr wrote:
> Also, if it's possible for you to incorporate the newly integrated
> oes-texture-half-float conformance tests (see
> LayoutTests/webgl/generate-webgl-tests.py), that would be helpful. You'll need
> to temporarily unskip the webgl/ tests in LayoutTests/TestExpectations in
order
> to make sure the new tests are working.

Hi, Kenneth. Thanks for your comments.
I have made changes accordingly to pass value instead of pointer. For importing
test cases from khronos WebGL conformance test, I'd like to defer until the
patch https://codereview.chromium.org/14366040/ landed. Since the test cases
depends on "ext.HALF_FLOAT_OES" which will be introduced in patch 14366040.

[Ken Russell (switch to Gerrit), 2013-04-24 23:15:47]

https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
File Source/core/platform/graphics/GraphicsContext3D.cpp (right):

https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
Source/core/platform/graphics/GraphicsContext3D.cpp:1729: };
The temporary arrays here and throughout are no longer necessary since
convertFloatToHalfFloat now passes its arguments by value.

[Jun Jiang, 2013-04-25 10:26:47]

On 2013/04/24 23:15:47, kbr wrote:
>
https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
> File Source/core/platform/graphics/GraphicsContext3D.cpp (right):
> 
>
https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
> Source/core/platform/graphics/GraphicsContext3D.cpp:1729: };
> The temporary arrays here and throughout are no longer necessary since
> convertFloatToHalfFloat now passes its arguments by value.
done.

[greggman, 2013-04-25 16:26:35]

On 2013/04/25 10:26:47, Jun Jiang wrote:
> On 2013/04/24 23:15:47, kbr wrote:
> >
>
https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
> > File Source/core/platform/graphics/GraphicsContext3D.cpp (right):
> > 
> >
>
https://codereview.chromium.org/13842017/diff/6001/Source/core/platform/graph...
> > Source/core/platform/graphics/GraphicsContext3D.cpp:1729: };
> > The temporary arrays here and throughout are no longer necessary since
> > convertFloatToHalfFloat now passes its arguments by value.
> done.

Why are we adding these tests to fast/canvas/webgl? I thought the idea was to
delete those tests and use the ones in LayoutTests/webgl

How about enabling the ones over there?

[Ken Russell (switch to Gerrit), 2013-04-25 19:54:58]

On 2013/04/25 16:26:35, greggman wrote:
> Why are we adding these tests to fast/canvas/webgl? I thought the idea was to
> delete those tests and use the ones in LayoutTests/webgl
> 
> How about enabling the ones over there?

Yes, the tests should be added under webgl/ using the generate-webgl-tests.py
script, not under fast/canvas/webgl.

[Ken Russell (switch to Gerrit), 2013-04-25 19:56:07]

The code changes LGTM but the tests should be added under webgl/ .

[Jun Jiang, 2013-04-26 01:32:01]

On 2013/04/25 19:56:07, kbr wrote:
> The code changes LGTM but the tests should be added under webgl/ .

Yes, I tried to add these tests to LayoutTests/webgl/conformance/extensions/ in
the same way as oex-texture-float.html using iframe. But I find it can not catch
any sub failures and it always pass. Has anyone met similar issue?

[Ken Russell (switch to Gerrit), 2013-04-26 01:35:10]

On 2013/04/26 01:32:01, Jun Jiang wrote:
> On 2013/04/25 19:56:07, kbr wrote:
> > The code changes LGTM but the tests should be added under webgl/ .
> 
> Yes, I tried to add these tests to LayoutTests/webgl/conformance/extensions/
in
> the same way as oex-texture-float.html using iframe. But I find it can not
catch
> any sub failures and it always pass. Has anyone met similar issue?

Unfortunately, currently, the webgl/ tests are all skipped in
LayoutTests/TestExpectations. In order to verify the test you'll need to
temporarily comment out the exclusion of webgl/ in TestExpectations.  We aren't
yet ready to these tests on by default but would like them to be ready to go
when we are.

[Jun Jiang, 2013-04-26 01:47:08]

On 2013/04/26 01:35:10, kbr wrote:
> On 2013/04/26 01:32:01, Jun Jiang wrote:
> > On 2013/04/25 19:56:07, kbr wrote:
> > > The code changes LGTM but the tests should be added under webgl/ .
> > 
> > Yes, I tried to add these tests to LayoutTests/webgl/conformance/extensions/
> in
> > the same way as oex-texture-float.html using iframe. But I find it can not
> catch
> > any sub failures and it always pass. Has anyone met similar issue?
> 
> Unfortunately, currently, the webgl/ tests are all skipped in
> LayoutTests/TestExpectations. In order to verify the test you'll need to
> temporarily comment out the exclusion of webgl/ in TestExpectations.  We
aren't
> yet ready to these tests on by default but would like them to be ready to go
> when we are.

Hi, Kenneth. Thanks for your comments. I think that's why my initial try fail
now and I will move the tests back to LayoutTests/webgl/.

[Jun Jiang, 2013-04-26 09:40:13]

On 2013/04/26 01:47:08, Jun Jiang wrote:
> On 2013/04/26 01:35:10, kbr wrote:
> > On 2013/04/26 01:32:01, Jun Jiang wrote:
> > > On 2013/04/25 19:56:07, kbr wrote:
> > > > The code changes LGTM but the tests should be added under webgl/ .
> > > 
> > > Yes, I tried to add these tests to
LayoutTests/webgl/conformance/extensions/
> > in
> > > the same way as oex-texture-float.html using iframe. But I find it can not
> > catch
> > > any sub failures and it always pass. Has anyone met similar issue?
> > 
> > Unfortunately, currently, the webgl/ tests are all skipped in
> > LayoutTests/TestExpectations. In order to verify the test you'll need to
> > temporarily comment out the exclusion of webgl/ in TestExpectations.  We
> aren't
> > yet ready to these tests on by default but would like them to be ready to go
> > when we are.
> 
> Hi, Kenneth. Thanks for your comments. I think that's why my initial try fail
> now and I will move the tests back to LayoutTests/webgl/.

Done.

[Ken Russell (switch to Gerrit), 2013-04-26 18:44:58]

Committed in https://codereview.chromium.org/14113033 /
https://src.chromium.org/viewvc/blink?view=rev&revision=149215 .

[Nayan, 2013-05-06 20:14:20]

On 2013/04/26 18:44:58, kbr wrote:
> Committed in https://codereview.chromium.org/14113033 /
> https://src.chromium.org/viewvc/blink?view=rev&revision=149215 .

Thanks Jun for refining oes-texture-half-float implementation, logic of
converting from float to half-float looks really great. :) Sorry for leaving
this work half-baked, I was away from blink/webkit of late.