Some Puffin http cleanup (#236)

### Checklist

* [X] I have read the [Contributor Guide](../CONTRIBUTING.md)
* [X] I have read and agree to the [Code of
Conduct](../CODE_OF_CONDUCT.md)
* [X] I have added a description of my changes and why I'd like them
included in the section below

### Description of Changes

Some small cleanup of scopes collection management in serialization and
`puffin_http`.
- replace `FrameView` var by `ScopeCollection` in `PuffinServerImpl`,
the other members of FrameView wasn't used.
- use an Option<&ScopeCollection> as parameter of FrameData.write_into
instead of `&ScopeCollection` + a boolean.

I think this changes make the code easier to understand.

Author: gwen-lg

puffin/src/frame_data.rs

@@ -568,8 +568,7 @@ impl FrameData {
     #[cfg(feature = "serialization")]
     pub fn write_into(
         &self,
-        scope_collection: &crate::ScopeCollection,
-        send_all_scopes: bool,
+        scope_collection: Option<&crate::ScopeCollection>,
         write: &mut impl std::io::Write,
     ) -> anyhow::Result<()> {
         use bincode::Options as _;
@@ -589,7 +588,7 @@ impl FrameData {
         write.write_u8(packed_streams.compression_kind as u8)?;
         write.write_all(&packed_streams.bytes)?;
 
-        let to_serialize_scopes: Vec<_> = if send_all_scopes {
+        let to_serialize_scopes: Vec<_> = if let Some(scope_collection) = scope_collection {
             scope_collection.scopes_by_id().values().cloned().collect()
         } else {
             self.scope_delta.clone()

puffin/src/profile_view.rs

@@ -26,6 +26,7 @@ pub struct FrameView {
     /// Maintain stats as we add/remove frames
     stats: FrameStats,
 
+    /// Collect all scope infos(id/name) from the start of the profiling.
     scope_collection: ScopeCollection,
 }
 
@@ -229,7 +230,7 @@ impl FrameView {
         write.write_all(b"PUF0")?;
 
         for frame in self.all_uniq() {
-            frame.write_into(&self.scope_collection, false, write)?;
+            frame.write_into(None, write)?;
         }
         Ok(())
     }

puffin_http/src/server.rs

@@ -1,5 +1,5 @@
 use anyhow::Context as _;
-use puffin::{FrameSinkId, FrameView, GlobalProfiler};
+use puffin::{FrameSinkId, GlobalProfiler, ScopeCollection};
 use std::{
     io::Write,
     net::{SocketAddr, TcpListener, TcpStream},
@@ -249,11 +249,10 @@ impl Server {
                     clients: Default::default(),
                     num_clients: num_clients_cloned,
                     send_all_scopes: false,
-                    frame_view: Default::default(),
+                    scope_collection: Default::default(),
                 };
 
                 while let Ok(frame) = rx.recv() {
-                    server_impl.frame_view.add_frame(frame.clone());
                     if let Err(err) = server_impl.accept_new_clients() {
                         log::warn!("puffin server failure: {}", err);
                     }
@@ -325,7 +324,7 @@ struct PuffinServerImpl {
     clients: Vec<Client>,
     num_clients: Arc<AtomicUsize>,
     send_all_scopes: bool,
-    frame_view: FrameView,
+    scope_collection: ScopeCollection,
 }
 
 impl PuffinServerImpl {
@@ -372,18 +371,25 @@ impl PuffinServerImpl {
         }
         puffin::profile_function!();
 
+        // Keep scope_collection up-to-date
+        frame.scope_delta.iter().for_each(|new_scope| {
+            self.scope_collection.insert(new_scope.clone());
+        });
+
         let mut packet = vec![];
 
         packet
             .write_all(&crate::PROTOCOL_VERSION.to_le_bytes())
             .unwrap();
 
+        let scope_collection = if self.send_all_scopes {
+            Some(&self.scope_collection)
+        } else {
+            None
+        };
+
         frame
-            .write_into(
-                self.frame_view.scope_collection(),
-                self.send_all_scopes,
-                &mut packet,
-            )
+            .write_into(scope_collection, &mut packet)
             .context("Encode puffin frame")?;
         self.send_all_scopes = false;