Auto merge of #16893 - MortimerGoro:webgl_extensions, r=emilio

Implement WebGL extensions

<!-- Please describe your changes on the following line: -->

This PR provides the base for implementing WebGL extensions. It comes with the following ones already implemented and passing all related WebGL conformance tests:

- OES_texture_float
- OES_texture_float_linear
- OES_texture_half_float
- OES_texture_half_float_linear
- OES_vertex_array_object

I'll submit other extensions like compressed textures in a separate PR to ease the review process. I included the 5 extensions in this PR because it's easier to show/review how the WebGL extension base works.

To pass all OES_texture_float_xxx tests I had to add some missing format conversions in WebGLRenderingContext.rs

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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7 files changed, 74 insertions, 1 deletions

diff --git a/components/script/dom/webidls/OESTextureFloat.webidl b/components/script/dom/webidls/OESTextureFloat.webidl
new file mode 100644
index 00000000000..518bd8f9050
--- /dev/null
+++ b/components/script/dom/webidls/OESTextureFloat.webidl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_texture_float/
+ */
+
+[NoInterfaceObject]
+interface OESTextureFloat {
+};
diff --git a/components/script/dom/webidls/OESTextureFloatLinear.webidl b/components/script/dom/webidls/OESTextureFloatLinear.webidl
new file mode 100644
index 00000000000..3ac2e2758f4
--- /dev/null
+++ b/components/script/dom/webidls/OESTextureFloatLinear.webidl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_texture_float_linear/
+ */
+
+[NoInterfaceObject]
+interface OESTextureFloatLinear {
+};
diff --git a/components/script/dom/webidls/OESTextureHalfFloat.webidl b/components/script/dom/webidls/OESTextureHalfFloat.webidl
new file mode 100644
index 00000000000..802d87d2b82
--- /dev/null
+++ b/components/script/dom/webidls/OESTextureHalfFloat.webidl
@@ -0,0 +1,12 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_texture_half_float/
+ */
+
+[NoInterfaceObject]
+interface OESTextureHalfFloat {
+    const GLenum HALF_FLOAT_OES = 0x8D61;
+};
diff --git a/components/script/dom/webidls/OESTextureHalfFloatLinear.webidl b/components/script/dom/webidls/OESTextureHalfFloatLinear.webidl
new file mode 100644
index 00000000000..3a7826ad824
--- /dev/null
+++ b/components/script/dom/webidls/OESTextureHalfFloatLinear.webidl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_texture_half_float_linear/
+ */
+
+[NoInterfaceObject]
+interface OESTextureHalfFloatLinear {
+};
diff --git a/components/script/dom/webidls/OESVertexArrayObject.webidl b/components/script/dom/webidls/OESVertexArrayObject.webidl
new file mode 100644
index 00000000000..cb73c57d558
--- /dev/null
+++ b/components/script/dom/webidls/OESVertexArrayObject.webidl
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+ */
+
+[NoInterfaceObject]
+interface OESVertexArrayObject {
+    const unsigned long VERTEX_ARRAY_BINDING_OES = 0x85B5;
+
+    WebGLVertexArrayObjectOES? createVertexArrayOES();
+    void deleteVertexArrayOES(WebGLVertexArrayObjectOES? arrayObject);
+    boolean isVertexArrayOES(WebGLVertexArrayObjectOES? arrayObject);
+    void bindVertexArrayOES(WebGLVertexArrayObjectOES? arrayObject);
+};
diff --git a/components/script/dom/webidls/WebGLRenderingContext.webidl b/components/script/dom/webidls/WebGLRenderingContext.webidl
index 0d4c14a05df..885ad9486bb 100644
--- a/components/script/dom/webidls/WebGLRenderingContext.webidl
+++ b/components/script/dom/webidls/WebGLRenderingContext.webidl
@@ -608,7 +608,7 @@ interface WebGLRenderingContextBase
 
     any getVertexAttrib(GLuint index, GLenum pname);
 
-    //[WebGLHandlesContextLoss] GLsizeiptr getVertexAttribOffset(GLuint index, GLenum pname);
+    [WebGLHandlesContextLoss] GLsizeiptr getVertexAttribOffset(GLuint index, GLenum pname);
 
     void hint(GLenum target, GLenum mode);
     [WebGLHandlesContextLoss] GLboolean isBuffer(WebGLBuffer? buffer);
diff --git a/components/script/dom/webidls/WebGLVertexArrayObjectOES.webidl b/components/script/dom/webidls/WebGLVertexArrayObjectOES.webidl
new file mode 100644
index 00000000000..9355cf4004e
--- /dev/null
+++ b/components/script/dom/webidls/WebGLVertexArrayObjectOES.webidl
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/*
+ * WebGL IDL definitions scraped from the Khronos specification:
+ * https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+ */
+
+[NoInterfaceObject]
+interface WebGLVertexArrayObjectOES: WebGLObject {
+};