[dart:_http] Fix potentially large List<int> allocation in _WebSocketPerMessageDeflate.processIncomingMessage

processIncomingMessage() was creating List<int> to hold uncompressed bytes,
which is very wastefull if size of the message is large (spending a word
for each byte).

Changed processIncomingMessage() to use BytesBuilder for uncompressed bytes.

This fixes flaky out of memory failure on service/get_vm_timeline_rpc_test with
bytecode in dartk-optcounter-linux-release-ia32 configuration. In that test size of
uncompressed message exceeded 130MB, causing 1GB memory allocation (512MB List
was expanded).

Change-Id: Ic5a78a13bd431f5ad97496907a84a3f7ba01c1fa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117121
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Alexander Markov <[email protected]>

Author: alexmarkov

sdk/lib/_http/websocket_impl.dart

@@ -601,19 +601,19 @@ class _WebSocketPerMessageDeflate {
     data.addAll(const [0x00, 0x00, 0xff, 0xff]);
 
     decoder.process(data, 0, data.length);
-    var result = <int>[];
+    final result = new BytesBuilder();
     List<int> out;
 
     while ((out = decoder.processed()) != null) {
-      result.addAll(out);
+      result.add(out);
     }
 
     if ((serverSide && clientNoContextTakeover) ||
         (!serverSide && serverNoContextTakeover)) {
       decoder = null;
     }
 
-    return new Uint8List.fromList(result);
+    return result.takeBytes();
   }
 
   List<int> processOutgoingMessage(List<int> msg) {

sdk_nnbd/lib/_http/websocket_impl.dart

@@ -601,19 +601,19 @@ class _WebSocketPerMessageDeflate {
     data.addAll(const [0x00, 0x00, 0xff, 0xff]);
 
     decoder.process(data, 0, data.length);
-    var result = <int>[];
+    final result = new BytesBuilder();
     List<int> out;
 
     while ((out = decoder.processed()) != null) {
-      result.addAll(out);
+      result.add(out);
     }
 
     if ((serverSide && clientNoContextTakeover) ||
         (!serverSide && serverNoContextTakeover)) {
       decoder = null;
     }
 
-    return new Uint8List.fromList(result);
+    return result.takeBytes();
   }
 
   List<int> processOutgoingMessage(List<int> msg) {