Auto merge of #11168 - daoshengmu:texSubImage2D, r=emilio

Implement WebGL TexSubImage2D

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

Either:
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because I have run the wpt test of texSubImage2D.html, and it works.

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

I have implemented ```TexSubImage2D``` follow [the spec](https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.8). This is my first version of implementation, and I notice I can reuse the code from ```TexImage2D```. Therefore, I would like to discuss make ```validate_tex_image2D_from_buffer``` and ```validate_tex_image2D_from_source``` to remove duplicate code.

Part of #10209

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="35" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/11168)
<!-- Reviewable:end -->

components/script/dom/webidls/WebGLRenderingContext.webidl

@@ -646,11 +646,11 @@ interface WebGLRenderingContextBase
     void texParameterf(GLenum target, GLenum pname, GLfloat param);
     void texParameteri(GLenum target, GLenum pname, GLint param);
 
-    //void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
-    //                   GLsizei width, GLsizei height,
-    //                   GLenum format, GLenum type, ArrayBufferView? pixels);
-    //void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
-    //                   GLenum format, GLenum type, TexImageSource? source); // May throw DOMException
+    void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
+                      GLsizei width, GLsizei height,
+                      GLenum format, GLenum type, optional object data);
+    void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
+                      GLenum format, GLenum type, TexImageSource? source); // May throw DOMException
 
     void uniform1f(WebGLUniformLocation? location, GLfloat x);
     //void uniform1fv(WebGLUniformLocation? location, Float32Array v);