Auto merge of #26697 - utsavoza:ugo/issue-11681/22-05-2020, r=jdm

Implement CanvasRenderingContext2d.fillText

The PR consists of broadly two main changes:
- Implementation of Canvas2dRenderingContext.font
- Basic implementation of Canvas2dRenderingContext.fillText

Although I am not fully sure about the long term goals for the canvas backend in Servo, I assumed limited scope for font and text handling (should support simple text drawing with font selection) in the current implementation as I believe a more complete implementation would eventually be brought in as a part of #22957.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #11681
- [x] There are tests for these changes

components/layout_thread/lib.rs

@@ -49,12 +49,13 @@ use layout::flow_ref::FlowRef;
 use layout::incremental::{RelayoutMode, SpecialRestyleDamage};
 use layout::layout_debug;
 use layout::parallel;
-use layout::query::{process_client_rect_query, process_element_inner_text_query};
 use layout::query::{
-    process_content_box_request, process_content_boxes_request, LayoutRPCImpl, LayoutThreadData,
+    process_client_rect_query, process_content_box_request, process_content_boxes_request,
+    process_element_inner_text_query, process_node_scroll_area_request,
+    process_node_scroll_id_request, process_offset_parent_query,
+    process_resolved_font_style_request, process_resolved_style_request, LayoutRPCImpl,
+    LayoutThreadData,
 };
-use layout::query::{process_node_scroll_area_request, process_node_scroll_id_request};
-use layout::query::{process_offset_parent_query, process_resolved_style_request};
 use layout::sequential;
 use layout::traversal::{
     construct_flows_at_ancestors, ComputeStackingRelativePositions, PreorderFlowTraversal,
@@ -558,6 +559,7 @@ impl LayoutThread {
                 scroll_id_response: None,
                 scroll_area_response: Rect::zero(),
                 resolved_style_response: String::new(),
+                resolved_font_style_response: None,
                 offset_parent_response: OffsetParentResponse::empty(),
                 scroll_offsets: HashMap::new(),
                 text_index_response: TextIndexResponse(None),
@@ -1231,6 +1233,9 @@ impl LayoutThread {
                         &QueryMsg::ElementInnerTextQuery(_) => {
                             rw_data.element_inner_text_response = String::new();
                         },
+                        &QueryMsg::ResolvedFontStyleQuery(..) => {
+                            rw_data.resolved_font_style_response = None;
+                        },
                         &QueryMsg::InnerWindowDimensionsQuery(_) => {
                             rw_data.inner_window_dimensions_response = None;
                         },
@@ -1498,6 +1503,7 @@ impl LayoutThread {
             &mut *rw_data,
             &mut layout_context,
             data.result.borrow_mut().as_mut().unwrap(),
+            document_shared_lock,
         );
     }
 
@@ -1507,6 +1513,7 @@ impl LayoutThread {
         rw_data: &mut LayoutThreadData,
         context: &mut LayoutContext,
         reflow_result: &mut ReflowComplete,
+        shared_lock: &SharedRwLock,
     ) {
         reflow_result.pending_images =
             std::mem::replace(&mut *context.pending_images.lock().unwrap(), vec![]);
@@ -1549,6 +1556,18 @@ impl LayoutThread {
                     rw_data.resolved_style_response =
                         process_resolved_style_request(context, node, pseudo, property, root_flow);
                 },
+                &QueryMsg::ResolvedFontStyleQuery(node, ref property, ref value) => {
+                    let node = unsafe { ServoLayoutNode::new(&node) };
+                    let url = self.url.clone();
+                    rw_data.resolved_font_style_response = process_resolved_font_style_request(
+                        context,
+                        node,
+                        value,
+                        property,
+                        url,
+                        shared_lock,
+                    );
+                },
                 &QueryMsg::OffsetParentQuery(node) => {
                     rw_data.offset_parent_response = process_offset_parent_query(node, root_flow);
                 },