Made it so you can specify the old gen heap size. (flutter/engine#15259)

engine/src/flutter/common/settings.cc

@@ -58,6 +58,7 @@ std::string Settings::ToString() const {
   stream << "assets_path: " << assets_path << std::endl;
   stream << "frame_rasterized_callback set: " << !!frame_rasterized_callback
          << std::endl;
+  stream << "old_gen_heap_size: " << old_gen_heap_size << std::endl;
   return stream.str();
 }
 

engine/src/flutter/common/settings.h

@@ -191,6 +191,13 @@ struct Settings {
   // the buffer must be as small as possible.
   std::shared_ptr<const fml::Mapping> persistent_isolate_data;
 
+  /// Max size of old gen heap size in MB, or 0 for unlimited, -1 for default
+  /// value.
+  ///
+  /// See also:
+  /// https://github.com/dart-lang/sdk/blob/ca64509108b3e7219c50d6c52877c85ab6a35ff2/runtime/vm/flag_list.h#L150
+  int64_t old_gen_heap_size = -1;
+
   std::string ToString() const;
 };
 

engine/src/flutter/runtime/dart_vm.cc

@@ -7,6 +7,7 @@
 #include <sys/stat.h>
 
 #include <mutex>
+#include <sstream>
 #include <vector>
 
 #include "flutter/common/settings.h"
@@ -111,6 +112,12 @@ static const char* kDartTraceStreamsArgs[] = {
     "--timeline_streams=Compiler,Dart,Debugger,Embedder,GC,Isolate,VM,API",
 };
 
+static std::string DartOldGenHeapSizeArgs(uint64_t heap_size) {
+  std::ostringstream oss;
+  oss << "--old_gen_heap_size=" << heap_size;
+  return oss.str();
+}
+
 constexpr char kFileUriPrefix[] = "file://";
 constexpr size_t kFileUriPrefixLength = sizeof(kFileUriPrefix) - 1;
 
@@ -366,6 +373,13 @@ DartVM::DartVM(std::shared_ptr<const DartVMData> vm_data,
     PushBackAll(&args, kDartTraceStartupArgs, fml::size(kDartTraceStartupArgs));
   }
 
+  std::string old_gen_heap_size_args;
+  if (settings_.old_gen_heap_size >= 0) {
+    old_gen_heap_size_args =
+        DartOldGenHeapSizeArgs(settings_.old_gen_heap_size);
+    args.push_back(old_gen_heap_size_args.c_str());
+  }
+
 #if defined(OS_FUCHSIA)
   PushBackAll(&args, kDartFuchsiaTraceArgs, fml::size(kDartFuchsiaTraceArgs));
   PushBackAll(&args, kDartTraceStreamsArgs, fml::size(kDartTraceStreamsArgs));

engine/src/flutter/runtime/dart_vm_unittests.cc

@@ -32,5 +32,15 @@ TEST_F(DartVMTest, SimpleIsolateNameServer) {
   ASSERT_TRUE(ns->RemoveIsolateNameMapping("foobar"));
 }
 
+TEST_F(DartVMTest, OldGenHeapSize) {
+  ASSERT_FALSE(DartVMRef::IsInstanceRunning());
+  auto settings = CreateSettingsForFixture();
+  settings.old_gen_heap_size = 1024;
+  auto vm = DartVMRef::Create(settings);
+  // There is no way to introspect on the heap size so we just assert the vm was
+  // created.
+  ASSERT_TRUE(vm);
+}
+
 }  // namespace testing
 }  // namespace flutter

engine/src/flutter/shell/platform/embedder/embedder.cc

@@ -664,6 +664,7 @@ FlutterEngineResult FlutterEngineInitialize(size_t version,
   settings.icu_data_path = icu_data_path;
   settings.assets_path = args->assets_path;
   settings.leak_vm = !SAFE_ACCESS(args, shutdown_dart_vm_when_done, false);
+  settings.old_gen_heap_size = SAFE_ACCESS(args, dart_old_gen_heap_size, -1);
 
   if (!flutter::DartVM::IsRunningPrecompiledCode()) {
     // Verify the assets path contains Dart 2 kernel assets.

engine/src/flutter/shell/platform/embedder/embedder.h

@@ -1114,6 +1114,13 @@ typedef struct {
   /// absence, platforms views in the scene are ignored and Flutter renders to
   /// the root surface as normal.
   const FlutterCompositor* compositor;
+
+  /// Max size of the old gen heap for the Dart VM in MB, or 0 for unlimited, -1
+  /// for default value.
+  ///
+  /// See also:
+  /// https://github.com/dart-lang/sdk/blob/ca64509108b3e7219c50d6c52877c85ab6a35ff2/runtime/vm/flag_list.h#L150
+  int64_t dart_old_gen_heap_size;
 } FlutterProjectArgs;
 
 //------------------------------------------------------------------------------