Undo texture unit code refactoring - it is ok to bind a texture to multiple locations
https://bugs.webkit.org/show_bug.cgi?id=122369
<rdar://problem/15158465>

Reviewed by Darin Adler.

The optimisation in r152351 (http://webkit.org/b/117868) incorrectly
assumes that a texture cannot be bound to more than one location.
That's true only within the same program object. It's legal to
address TEXTURE_BINDING_2D and TEXTURE_BINDING_CUBE_MAP with the
same texture in different programs.

See https://github.com/KhronosGroup/WebGL/pull/391 for more information.

This change reverts the optimisation, but also does some minor
cleanup (0 -> nullptr, class -> struct).

Covered by the following Khronos WebGL 1.0.1 tests, which
now pass:
- conformance/more/functions/texImage2DHTML.html
- conformance/more/functions/texSubImage2D.html
- conformance/more/functions/texSubImage2DHTML.html

* html/canvas/WebGLRenderingContext.cpp:
(WebCore::WebGLRenderingContext::~WebGLRenderingContext):
(WebCore::WebGLRenderingContext::reshape):
(WebCore::WebGLRenderingContext::bindTexture):
(WebCore::WebGLRenderingContext::deleteTexture):
(WebCore::WebGLRenderingContext::getParameter):
(WebCore::WebGLRenderingContext::handleNPOTTextures):
(WebCore::WebGLRenderingContext::validateTextureBinding):
(WebCore::WebGLRenderingContext::restoreCurrentTexture2D):
* html/canvas/WebGLRenderingContext.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@156970 268f45cc-cd09-0410-ab3c-d52691b4dbfc
[WebGL] program should not be able to link if a bad shader is attached
https://bugs.webkit.org/show_bug.cgi?id=94036

Reviewed by Darin Adler.

If you attempt to link a program when bad shaders are attached, the
link should fail. WebGL also requires that the previously linked
program should remain intact. We were doing the former, but not
the latter.

Fix this by not calling glLinkProgram if we know we have bad
shaders, and synthesize a bad link status instead.

Test: WebGL conformance test conformance/programs/program-test.html
(found in LayoutTests/webgl)

* html/canvas/WebGLRenderingContext.cpp:
(WebCore::WebGLRenderingContext::compileShader): Mark a shader as valid
if it compiled ok.
(WebCore::WebGLRenderingContext::linkProgram): Don't call into GraphicsContext3D::linkProgram
if we know that we don't have valid shaders.
* html/canvas/WebGLShader.cpp:
(WebCore::WebGLShader::WebGLShader): Initialize m_isValid.
* html/canvas/WebGLShader.h:
(WebCore::WebGLShader::isValid): New member variable getter and setter.
(WebCore::WebGLShader::setValid):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@156971 268f45cc-cd09-0410-ab3c-d52691b4dbfc