Auto merge of #13785 - gterzian:use_veqdequeu_in_servoparser, r=nox

switch to using DOMRefCell<VeqDeque<String>> for ServoParser::pending…

<!-- Please describe your changes on the following line: -->
The field ServoParser::pending_input should be a DOMRefCell<VeqDeque<String>>, this lets us use VecDeque::pop_front instead of Vec::remove in ServoParser::take_next_input_chunk.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #13690 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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…_input

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components/script/dom/bindings/trace.rs

@@ -78,7 +78,7 @@ use serde::{Deserialize, Serialize};
 use smallvec::SmallVec;
 use std::boxed::FnBox;
 use std::cell::{Cell, UnsafeCell};
-use std::collections::{BTreeMap, HashMap, HashSet};
+use std::collections::{BTreeMap, HashMap, HashSet, VecDeque};
 use std::hash::{BuildHasher, Hash};
 use std::ops::{Deref, DerefMut};
 use std::path::PathBuf;
@@ -208,6 +208,15 @@ impl<T: JSTraceable> JSTraceable for Vec<T> {
     }
 }
 
+impl<T: JSTraceable> JSTraceable for VecDeque<T> {
+    #[inline]
+    fn trace(&self, trc: *mut JSTracer) {
+        for e in &*self {
+            e.trace(trc);
+        }
+    }
+}
+
 impl<T: JSTraceable> JSTraceable for (T, T, T, T) {
     fn trace(&self, trc: *mut JSTracer) {
         self.0.trace(trc);

components/script/dom/servoparser/mod.rs

@@ -34,6 +34,7 @@ use profile_traits::time::{TimerMetadata, TimerMetadataFrameType};
 use profile_traits::time::{TimerMetadataReflowType, ProfilerCategory, profile};
 use script_thread::ScriptThread;
 use std::cell::Cell;
+use std::collections::VecDeque;
 use url::Url;
 use util::resource_files::read_resource_file;
 use xml5ever::tokenizer::XmlTokenizer;
@@ -51,7 +52,7 @@ pub struct ServoParser {
     /// does not correspond to a page load.
     pipeline: Option<PipelineId>,
     /// Input chunks received but not yet passed to the parser.
-    pending_input: DOMRefCell<Vec<String>>,
+    pending_input: DOMRefCell<VecDeque<String>>,
     /// The tokenizer of this parser.
     tokenizer: DOMRefCell<Tokenizer>,
     /// Whether to expect any further input from the associated network request.
@@ -78,7 +79,7 @@ impl ServoParser {
             reflector: Reflector::new(),
             document: JS::from_ref(document),
             pipeline: pipeline,
-            pending_input: DOMRefCell::new(vec![]),
+            pending_input: DOMRefCell::new(VecDeque::new()),
             tokenizer: DOMRefCell::new(tokenizer),
             last_chunk_received: Cell::new(last_chunk_state == LastChunkState::Received),
             suspended: Default::default(),
@@ -111,7 +112,7 @@ impl ServoParser {
     }
 
     fn push_input_chunk(&self, chunk: String) {
-        self.pending_input.borrow_mut().push(chunk);
+        self.pending_input.borrow_mut().push_back(chunk);
     }
 
     fn take_next_input_chunk(&self) -> Option<String> {
@@ -119,7 +120,7 @@ impl ServoParser {
         if pending_input.is_empty() {
             None
         } else {
-            Some(pending_input.remove(0))
+            pending_input.pop_front()
         }
     }