Remove offscreen_gl_context dependency from canvas_traits and script.

components/canvas_traits/webgl.rs

@@ -6,7 +6,6 @@ use euclid::{Rect, Size2D};
 use gleam::gl;
 use gleam::gl::Gl;
 use ipc_channel::ipc::{IpcBytesReceiver, IpcBytesSender, IpcSharedMemory};
-use offscreen_gl_context::{GLContextAttributes, GLLimits};
 use pixels::PixelFormat;
 use std::borrow::Cow;
 use std::fmt;
@@ -811,3 +810,27 @@ pub enum YAxisTreatment {
     AsIs,
     Flipped,
 }
+
+#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
+pub struct GLContextAttributes {
+    pub alpha: bool,
+    pub depth: bool,
+    pub stencil: bool,
+    pub antialias: bool,
+    pub premultiplied_alpha: bool,
+    pub preserve_drawing_buffer: bool,
+}
+
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub struct GLLimits {
+    pub max_vertex_attribs: u32,
+    pub max_tex_size: u32,
+    pub max_cube_map_tex_size: u32,
+    pub max_combined_texture_image_units: u32,
+    pub max_fragment_uniform_vectors: u32,
+    pub max_renderbuffer_size: u32,
+    pub max_texture_image_units: u32,
+    pub max_varying_vectors: u32,
+    pub max_vertex_texture_image_units: u32,
+    pub max_vertex_uniform_vectors: u32,
+}