servo: Merge #13470 - layout: Improve the interaction between baseline-offset-of-last-line-in-flow logic and inline absolute hypothetical boxes (from pcwalton:inline-absolute-hypothetical-baseline); r=notriddle

See commits for details. These changes place the heart icon on Twitter in the right place.

r? @notriddle

Source-Repo: https://github.com/servo/servo
Source-Revision: ccfc60161b8d92217b9f77040d6928d429bcbe9d

servo/components/layout/flow.rs

@@ -1404,7 +1404,9 @@ impl<'a> ImmutableFlowUtils for &'a Flow {
     fn baseline_offset_of_last_line_box_in_flow(self) -> Option<Au> {
         for kid in base(self).children.iter().rev() {
             if kid.is_inline_flow() {
-                return kid.as_inline().baseline_offset_of_last_line()
+                if let Some(baseline_offset) = kid.as_inline().baseline_offset_of_last_line() {
+                    return Some(baseline_offset)
+                }
             }
             if kid.is_block_like() &&
                     kid.as_block().formatting_context_type() == FormattingContextType::None &&

servo/components/layout/inline.rs

@@ -1262,13 +1262,16 @@ impl InlineFlow {
     }
 
     pub fn baseline_offset_of_last_line(&self) -> Option<Au> {
-        match self.lines.last() {
-            None => None,
-            Some(ref last_line) => {
-                Some(last_line.bounds.start.b + last_line.bounds.size.block -
-                     last_line.inline_metrics.depth_below_baseline)
+        // Find the last line that doesn't consist entirely of hypothetical boxes.
+        for line in self.lines.iter().rev() {
+            if (line.range.begin().get()..line.range.end().get()).any(|index| {
+                !self.fragments.fragments[index as usize].is_hypothetical()
+            }) {
+                return Some(line.bounds.start.b + line.bounds.size.block -
+                            line.inline_metrics.depth_below_baseline)
             }
         }
+        None
     }
 }
 
@@ -1451,7 +1454,6 @@ impl Flow for InlineFlow {
                                            self.minimum_depth_below_baseline);
         scanner.scan_for_lines(self, layout_context);
 
-
         // Now, go through each line and lay out the fragments inside.
         let line_count = self.lines.len();
         for (line_index, line) in self.lines.iter_mut().enumerate() {