Make HTMLCanvasElement::get_size return a Size2D<u32>

The changes keep trickling down.

components/canvas_traits/webgl.rs

@@ -36,10 +36,14 @@ pub struct WebGLCommandBacktrace {
 #[derive(Deserialize, Serialize)]
 pub enum WebGLMsg {
     /// Creates a new WebGLContext.
-    CreateContext(WebGLVersion, Size2D<i32>, GLContextAttributes,
-                  WebGLSender<Result<(WebGLCreateContextResult), String>>),
+    CreateContext(
+        WebGLVersion,
+        Size2D<u32>,
+        GLContextAttributes,
+        WebGLSender<Result<(WebGLCreateContextResult), String>>,
+    ),
     /// Resizes a WebGLContext.
-    ResizeContext(WebGLContextId, Size2D<i32>, WebGLSender<Result<(), String>>),
+    ResizeContext(WebGLContextId, Size2D<u32>, WebGLSender<Result<(), String>>),
     /// Drops a WebGLContext.
     RemoveContext(WebGLContextId),
     /// Runs a WebGLCommand in a specific WebGLContext.
@@ -141,10 +145,11 @@ impl WebGLMsgSender {
 
     /// Send a resize message
     #[inline]
-    pub fn send_resize(&self,
-                       size: Size2D<i32>,
-                       sender: WebGLSender<Result<(), String>>)
-                       -> WebGLSendResult {
+    pub fn send_resize(
+        &self,
+        size: Size2D<u32>,
+        sender: WebGLSender<Result<(), String>>,
+    ) -> WebGLSendResult {
         self.sender.send(WebGLMsg::ResizeContext(self.ctx_id, size, sender))
     }
 
@@ -224,7 +229,7 @@ pub enum WebGLCommand {
     RenderbufferStorage(u32, u32, i32, i32),
     ReadPixels(i32, i32, i32, i32, u32, u32, IpcBytesSender),
     SampleCoverage(f32, bool),
-    Scissor(i32, i32, i32, i32),
+    Scissor(i32, i32, u32, u32),
     StencilFunc(u32, i32, u32),
     StencilFuncSeparate(u32, u32, i32, u32),
     StencilMask(u32),