GN: Build app snapshots for the SDK tools.

runtime/bin/main.cc

Index: runtime/bin/main.cc
diff --git a/runtime/bin/main.cc b/runtime/bin/main.cc
index 10861340c162816ac3e1d4c67d8264fb2068cce5..8546f2b0a72cc14aa6bc781e223a4a44be93e417 100644
--- a/runtime/bin/main.cc
+++ b/runtime/bin/main.cc
@@ -775,6 +775,9 @@ static Dart_Handle EnvironmentCallback(Dart_Handle name) {
   }                                                                            \
 
 
+static void SnapshotOnExitHook(int64_t exit_code);
+
+
 // Returns true on success, false on failure.
 static Dart_Isolate CreateIsolateAndSetupHelper(const char* script_uri,
                                                 const char* main,
@@ -801,6 +804,10 @@ static Dart_Isolate CreateIsolateAndSetupHelper(const char* script_uri,
   IsolateData* isolate_data = new IsolateData(script_uri,
                                               package_root,
                                               packages_config);
+  if ((gen_snapshot_kind == kAppAfterRun) ||
+      (gen_snapshot_kind == kAppJITAfterRun)) {
+    isolate_data->set_exit_hook(SnapshotOnExitHook);
+  }
   Dart_Isolate isolate = Dart_CreateIsolate(script_uri,
                                             main,
                                             isolate_snapshot_buffer,
@@ -1521,6 +1528,16 @@ static void GenerateFullSnapshot() {
   }
 
 
+static void SnapshotOnExitHook(int64_t exit_code) {
+  if (gen_snapshot_kind == kAppAfterRun) {
+    GenerateFullSnapshot();
+  } else {
+    Dart_PrecompileJIT();
+    GeneratePrecompiledJITSnapshot();
+  }
+}
+
+
 bool RunMainIsolate(const char* script_name,
                     CommandLineOptions* dart_options) {
   // Call CreateIsolateAndSetup which creates an isolate and loads up