Refactor validation checks for texture uploads
https://bugs.webkit.org/show_bug.cgi?id=111012

Patch by Jun Jiang <jun.a.jiang@intel.com> on 2013-03-27
Reviewed by Kenneth Russell.

Move the validation checks to the entry level of tex{Sub}Image2D, return early for invalid parameters and avoid duplicated checks.
Moreover, turn all the validation checks at the bottom level - tex{Sub}Image2DBase into assertions.

Already covered by current tests.

* html/canvas/WebGLRenderingContext.cpp:
(WebCore::WebGLRenderingContext::copyTexSubImage2D):
(WebCore::WebGLRenderingContext::texImage2DBase):
(WebCore::WebGLRenderingContext::texImage2DImpl):
(WebCore::WebGLRenderingContext::validateTexFunc): A helper function for tex{Sub}Image2D to check input parameters.
(WebCore::WebGLRenderingContext::texImage2D):
(WebCore::WebGLRenderingContext::texSubImage2DBase):
(WebCore::WebGLRenderingContext::texSubImage2DImpl):
(WebCore::WebGLRenderingContext::texSubImage2D):
(WebCore::WebGLRenderingContext::validateHTMLImageElement):
(WebCore::WebGLRenderingContext::validateHTMLCanvasElement):
(WebCore::WebGLRenderingContext::validateHTMLVideoElement):
* html/canvas/WebGLRenderingContext.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147042 268f45cc-cd09-0410-ab3c-d52691b4dbfc