CoreJIT snapshots without training.

runtime/bin/BUILD.gn

Index: runtime/bin/BUILD.gn
diff --git a/runtime/bin/BUILD.gn b/runtime/bin/BUILD.gn
index 4f30948dc15643e0f1ae14c7252faf25a859d2d0..656e3011f2ade66882e7efd1d1e979ce9c4abbb6 100644
--- a/runtime/bin/BUILD.gn
+++ b/runtime/bin/BUILD.gn
@@ -460,15 +460,25 @@ action("generate_snapshot_bin") {
     "../bin:gen_snapshot($host_toolchain)",
   ]
 
-  vm_isolate_snapshot = "$target_gen_dir/vm_isolate_snapshot.bin"
-  isolate_snapshot = "$target_gen_dir/isolate_snapshot.bin"
+  vm_snapshot_data = "$target_gen_dir/vm_snapshot_data.bin"
+  vm_snapshot_instructions = "$target_gen_dir/vm_snapshot_instructions.bin"
+  isolate_snapshot_data = "$target_gen_dir/isolate_snapshot_data.bin"
+  isolate_snapshot_instructions =
+      "$target_gen_dir/isolate_snapshot_instructions.bin"
   gen_snapshot_stamp_file = "$target_gen_dir/gen_snapshot.stamp"
   outputs = [
-    vm_isolate_snapshot,
-    isolate_snapshot,
+    vm_snapshot_data,
+    vm_snapshot_instructions,
+    isolate_snapshot_data,
+    isolate_snapshot_instructions,
     gen_snapshot_stamp_file,
   ]
 
+  snapshot_kind = "core"
+
+  # Putting code in the core snapshot breaks tests that use non-default flags.
+  # snapshot_kind = "core-jit"
+
   gen_snapshot_dir =
       get_label_info("../bin:gen_snapshot($host_toolchain)", "root_out_dir")
 
@@ -477,13 +487,15 @@ action("generate_snapshot_bin") {
     "--executable",
     rebase_path("$gen_snapshot_dir/gen_snapshot"),
     "--snapshot_kind",
-    "core",
+    snapshot_kind,
     "--vm_output_bin",
-    rebase_path(vm_isolate_snapshot, root_build_dir),
+    rebase_path(vm_snapshot_data, root_build_dir),
+    "--vm_instructions_output_bin",
+    rebase_path(vm_snapshot_instructions, root_build_dir),
     "--isolate_output_bin",
-    rebase_path(isolate_snapshot, root_build_dir),
-    "--target_os",
-    current_os,
+    rebase_path(isolate_snapshot_data, root_build_dir),
+    "--isolate_instructions_output_bin",
+    rebase_path(isolate_snapshot_instructions, root_build_dir),
     "--timestamp_file",
     rebase_path(gen_snapshot_stamp_file, root_build_dir),
   ]
@@ -529,15 +541,17 @@ bin_to_assembly("vm_snapshot_data_assembly") {
   deps = [
     ":generate_snapshot_bin",
   ]
-  input = "$target_gen_dir/vm_isolate_snapshot.bin"
+  input = "$target_gen_dir/vm_snapshot_data.bin"
   output = "$target_gen_dir/vm_snapshot_data.S"
   symbol = "kDartVmSnapshotData"
   executable = false
 }
 
 bin_to_assembly("vm_snapshot_instructions_assembly") {
-  deps = []
-  input = "../tools/empty.bin"
+  deps = [
+    ":generate_snapshot_bin",
+  ]
+  input = "$target_gen_dir/vm_snapshot_instructions.bin"
   output = "$target_gen_dir/vm_snapshot_instructions.S"
   symbol = "kDartVmSnapshotInstructions"
   executable = true
@@ -547,15 +561,17 @@ bin_to_assembly("isolate_snapshot_data_assembly") {
   deps = [
     ":generate_snapshot_bin",
   ]
-  input = "$target_gen_dir/isolate_snapshot.bin"
+  input = "$target_gen_dir/isolate_snapshot_data.bin"
   output = "$target_gen_dir/isolate_snapshot_data.S"
   symbol = "kDartCoreIsolateSnapshotData"
   executable = false
 }
 
 bin_to_assembly("isolate_snapshot_instructions_assembly") {
-  deps = []
-  input = "../tools/empty.bin"
+  deps = [
+    ":generate_snapshot_bin",
+  ]
+  input = "$target_gen_dir/isolate_snapshot_instructions.bin"
   output = "$target_gen_dir/isolate_snapshot_instructions.S"
   symbol = "kDartCoreIsolateSnapshotInstructions"
   executable = true