Compute profiling time range from samples and markers

This commit adds `profilingStartTime` and `profilingEndTime` fields
to the profile metadata, computed from all sample timestamps and
marker start/end times across all threads.

Author: nordzilla

fxprof-processed-profile/src/marker_table.rs

@@ -106,6 +106,14 @@ impl MarkerTable {
         self
     }
 
+    pub fn start_times(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.marker_starts.iter().copied().flatten()
+    }
+
+    pub fn end_times(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.marker_ends.iter().copied().flatten()
+    }
+
     pub fn as_serializable<'a>(
         &'a self,
         schemas: &'a [InternalMarkerSchema],

fxprof-processed-profile/src/profile.rs

@@ -1425,6 +1425,22 @@ impl Profile {
         }
     }
 
+    fn compute_profiling_time_range(&self) -> Option<(Timestamp, Timestamp)> {
+        self.threads
+            .iter()
+            .flat_map(|thread| {
+                thread
+                    .sample_timestamps()
+                    .chain(thread.marker_start_times())
+                    .chain(thread.marker_end_times())
+            })
+            .fold(None, |acc, timestamp| {
+                acc.map_or(Some((timestamp, timestamp)), |(min, max)| {
+                    Some((min.min(timestamp), max.max(timestamp)))
+                })
+            })
+    }
+
     fn contains_js_frame(&self) -> bool {
         self.threads.iter().any(|t| t.contains_js_frame())
     }
@@ -1497,6 +1513,12 @@ impl Serialize for SerializableProfileMeta<'_> {
             }
             None => {}
         }
+
+        if let Some((start, end)) = self.0.compute_profiling_time_range() {
+            map.serialize_entry("profilingStartTime", &start)?;
+            map.serialize_entry("profilingEndTime", &end)?;
+        }
+
         map.serialize_entry("symbolicated", &self.0.symbolicated)?;
         map.serialize_entry("pausedRanges", &[] as &[()])?;
         map.serialize_entry("version", &24)?; // this version is ignored, only "preprocessedProfileVersion" is used

fxprof-processed-profile/src/sample_table.rs

@@ -105,6 +105,10 @@ impl SampleTable {
         self.sample_weight_type = t;
     }
 
+    pub fn timestamps(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.sample_timestamps.iter().copied()
+    }
+
     pub fn modify_last_sample(&mut self, timestamp: Timestamp, weight: i32) {
         *self.sample_weights.last_mut().unwrap() += weight;
         *self.sample_timestamps.last_mut().unwrap() = timestamp;

fxprof-processed-profile/src/thread.rs

@@ -194,6 +194,18 @@ impl Thread {
         self.frame_interner.gather_used_rvas(collector);
     }
 
+    pub fn sample_timestamps(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.samples.timestamps()
+    }
+
+    pub fn marker_start_times(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.markers.start_times()
+    }
+
+    pub fn marker_end_times(&self) -> impl Iterator<Item = Timestamp> + use<'_> {
+        self.markers.end_times()
+    }
+
     pub fn cmp_for_json_order(&self, other: &Thread) -> Ordering {
         let ordering = (!self.is_main).cmp(&(!other.is_main));
         if ordering != Ordering::Equal {

fxprof-processed-profile/tests/integration_tests/main.rs

@@ -344,6 +344,8 @@ fn profile_without_js() {
                 "time": "ms"
               },
               "startTime": 1636162232627.0,
+              "profilingStartTime": 0.0,
+              "profilingEndTime": 3.0,
               "symbolicated": false,
               "pausedRanges": [],
               "version": 24,
@@ -1020,6 +1022,8 @@ fn profile_with_js() {
                 "time": "ms"
               },
               "startTime": 1636162232627.0,
+              "profilingStartTime": 1.0,
+              "profilingEndTime": 1.0,
               "symbolicated": false,
               "pausedRanges": [],
               "version": 24,
@@ -1277,6 +1281,8 @@ fn profile_counters_with_sorted_processes() {
                 "time": "ms"
               },
               "startTime": 1636162232627.0,
+              "profilingStartTime": 0.0,
+              "profilingEndTime": 1.0,
               "symbolicated": true,
               "pausedRanges": [],
               "version": 24,
@@ -1590,6 +1596,8 @@ fn test_flow_marker_fields() {
                 "time": "ms"
               },
               "startTime": 1636162232627.0,
+              "profilingStartTime": 10.0,
+              "profilingEndTime": 10.0,
               "symbolicated": false,
               "pausedRanges": [],
               "version": 24,