Use more WebRender types in gfx/display_list

This uses floating-point (Layout) coordinates in where possible.
Replace NormalBorder struct with WebRender equivalent.
Remove ToPointF and ToRectF traits.
Convert border RepeatKeyword with ToLayout.
Add some definitions to malloc_size_of for WebRender types.

components/layout/display_list/background.rs

@@ -23,7 +23,7 @@ use style::values::generics::image::EndingShape as GenericEndingShape;
 use style::values::generics::image::GradientItem as GenericGradientItem;
 use style::values::specified::background::RepeatKeyword;
 use style::values::specified::position::{X, Y};
-use webrender_api::GradientStop;
+use webrender_api::{ExtendMode, GradientStop};
 
 /// A helper data structure for gradients.
 #[derive(Clone, Copy)]
@@ -370,6 +370,14 @@ fn convert_gradient_stops(gradient_items: &[GradientItem], total_length: Au) ->
     stops
 }
 
+fn as_gradient_extend_mode(repeating: bool) -> ExtendMode {
+    if repeating {
+        ExtendMode::Repeat
+    } else {
+        ExtendMode::Clamp
+    }
+}
+
 pub fn convert_linear_gradient(
     size: Size2D<Au>,
     stops: &[GradientItem],
@@ -431,10 +439,10 @@ pub fn convert_linear_gradient(
     let center = Point2D::new(size.width / 2, size.height / 2);
 
     display_list::Gradient {
-        start_point: center - delta,
-        end_point: center + delta,
+        start_point: (center - delta).to_layout(),
+        end_point: (center + delta).to_layout(),
         stops: stops,
-        repeating: repeating,
+        extend_mode: as_gradient_extend_mode(repeating),
     }
 }
 
@@ -473,10 +481,10 @@ pub fn convert_radial_gradient(
     }
 
     display_list::RadialGradient {
-        center: center,
-        radius: radius,
+        center: center.to_layout(),
+        radius: radius.to_layout(),
         stops: stops,
-        repeating: repeating,
+        extend_mode: as_gradient_extend_mode(repeating),
     }
 }