implement PerformanceObserverInit.buffered (fixes #18108)

components/script/dom/performance.rs

@@ -18,6 +18,7 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use script_thread::{Runnable, ScriptThread};
 use std::cell::Cell;
+use std::cmp::Ordering;
 use time;
 
 /// Implementation of a list of PerformanceEntry items shared by the
@@ -51,6 +52,16 @@ impl PerformanceEntryList {
             entry_type.as_ref().map_or(true, |type_| *e.entry_type() == *type_)
         ).map(|e| e.clone()).collect()
     }
+
+    pub fn get_entries_by_name_and_type(&self, name: Option<DOMString>, entry_type: Option<DOMString>)
+        -> Vec<Root<PerformanceEntry>> {
+        let mut res = self.entries.iter().filter(|e|
+            name.as_ref().map_or(true, |name_| *e.name() == *name_) &&
+            entry_type.as_ref().map_or(true, |type_| *e.entry_type() == *type_)
+        ).map(|e| e.clone()).collect::<Vec<Root<PerformanceEntry>>>();
+        res.sort_by(|a, b| a.start_time().partial_cmp(&b.start_time()).unwrap_or(Ordering::Equal));
+        res
+    }
 }
 
 impl IntoIterator for PerformanceEntryList {
@@ -106,7 +117,17 @@ impl Performance {
     /// observed entry types.
     pub fn add_observer(&self,
                         observer: &DOMPerformanceObserver,
-                        entry_types: Vec<DOMString>) {
+                        entry_types: Vec<DOMString>,
+                        buffered: bool) {
+        if buffered {
+            let entries = self.entries.borrow();
+            let mut new_entries = entry_types.iter()
+                            .flat_map(|e| entries.get_entries_by_name_and_type(None, Some(e.clone())))
+                            .collect::<DOMPerformanceEntryList>();
+            let mut obs_entries = observer.entries();
+            obs_entries.append(&mut new_entries);
+            observer.set_entries(obs_entries);
+        }
         let mut observers = self.observers.borrow_mut();
         match observers.iter().position(|o| &(*o.observer) == observer) {
             // If the observer is already in the list, we only update the observed