webgl: Implement multiple calls and improve error detection

This commit implements WebGL's:
 * cullFace
 * frontFace
 * enable
 * disable
 * depthMask
 * colorMask
 * clearDepth
 * clearStencil
 * depthFunc
 * depthRange
 * hint
 * lineWidth
 * pixelStorei
 * polygonOffset
 * texParameteri
 * texParameterf
 * texImage2D (partially)

It inlines a lot of OpenGL calls to keep the file
`components/canvas/webgl_paint_task.rs` as small as possible while
keeping readability.

It also improves error detection on previous calls, and sets node damage
on the canvas in the drawing calls.

It adds a `TexImage2D` reftest, even though it's not enabled because:
 * WebGL paints the image when it loads (asynchronously), so the reftest doesn't wait for it and it finishes early
 * If we change the source for the base64 src of the image it works as expected in non-headless mode, but the test harness locks

components/canvas_traits/lib.rs

@@ -128,6 +128,16 @@ pub enum CanvasWebGLMsg {
     BufferData(u32, Vec<f32>, u32),
     Clear(u32),
     ClearColor(f32, f32, f32, f32),
+    ClearDepth(f64),
+    ClearStencil(i32),
+    ColorMask(bool, bool, bool, bool),
+    CullFace(u32),
+    FrontFace(u32),
+    DepthFunc(u32),
+    DepthMask(bool),
+    DepthRange(f64, f64),
+    Enable(u32),
+    Disable(u32),
     CompileShader(u32),
     CreateBuffer(IpcSender<Option<NonZero<u32>>>),
     CreateFramebuffer(IpcSender<Option<NonZero<u32>>>),
@@ -151,12 +161,19 @@ pub enum CanvasWebGLMsg {
     GetShaderParameter(u32, u32, IpcSender<WebGLShaderParameter>),
     GetAttribLocation(u32, String, IpcSender<Option<i32>>),
     GetUniformLocation(u32, String, IpcSender<Option<i32>>),
+    PolygonOffset(f32, f32),
+    Hint(u32, u32),
+    LineWidth(f32),
+    PixelStorei(u32, i32),
     LinkProgram(u32),
     ShaderSource(u32, String),
     Uniform4fv(i32, Vec<f32>),
     UseProgram(u32),
-    VertexAttribPointer2f(u32, i32, bool, i32, i64),
+    VertexAttribPointer2f(u32, i32, bool, i32, u32),
     Viewport(i32, i32, i32, i32),
+    TexImage2D(u32, i32, i32, i32, i32, u32, u32, Vec<u8>),
+    TexParameteri(u32, u32, i32),
+    TexParameterf(u32, u32, f32),
     DrawingBufferWidth(IpcSender<i32>),
     DrawingBufferHeight(IpcSender<i32>),
 }