Add an off-by-default flag for background compilation

sky/engine/core/script/dart_init.cc

@@ -72,9 +72,6 @@ static const char* kDartArgs[] = {
     // default profile period to 100Hz. This number is suitable for older
     // Raspberry Pi devices but quite low for current smartphones.
     "--profile_period=1000",
-    // Background compilation isn't quite ready, but this flag turns it on if we
-    // want to experiment with it.
-    // "--background_compilation",
 #if (WTF_OS_IOS || WTF_OS_MACOSX)
     // On platforms where LLDB is the primary debugger, SIGPROF signals
     // overwhelm LLDB.
@@ -82,6 +79,12 @@ static const char* kDartArgs[] = {
 #endif
 };
 
+// Background compilation isn't quite ready, but this flag turns it on if we
+// want to experiment with it.
+static const char* kDartBackgroundCompilationArgs[]{
+    "--background_compilation",
+};
+
 static const char* kDartPrecompilationArgs[]{
     "--precompilation",
 };
@@ -300,6 +303,9 @@ void InitDartVM() {
   if (enable_checked_mode)
     args.append(kDartCheckedModeArgs, arraysize(kDartCheckedModeArgs));
 
+  if (SkySettings::Get().enable_background_compilation)
+    args.append(kDartBackgroundCompilationArgs, arraysize(kDartBackgroundCompilationArgs));
+
   if (SkySettings::Get().start_paused)
     args.append(kDartStartPausedArgs, arraysize(kDartStartPausedArgs));
 

sky/engine/public/platform/sky_settings.h

@@ -14,6 +14,7 @@ struct SkySettings {
   uint32_t observatory_port = 8181;
   bool start_paused = false;
   bool enable_dart_checked_mode = false;
+  bool enable_background_compilation = false;
 
   static const SkySettings& Get();
   static void Set(const SkySettings& settings);

sky/shell/platform/android/org/domokit/sky/shell/SkyActivity.java

@@ -42,6 +42,9 @@ public class SkyActivity extends Activity {
         if (intent.getBooleanExtra("enable-checked-mode", false)) {
             args.add("--enable-checked-mode");
         }
+        if (intent.getBooleanExtra("enable-background-compilation", false)) {
+            args.add("--enable-background-compilation");
+        }
         if (intent.getBooleanExtra("trace-startup", false)) {
             args.add("--trace-startup");
         }

sky/shell/platform/mojo/main_mojo.cc

@@ -22,7 +22,6 @@ namespace sky {
 namespace shell {
 namespace {
 
-// Instruct the DartVM to report type errors.
 const char kEnableCheckedMode[] = "--enable-checked-mode";
 
 }  // namespace

sky/shell/shell.cc

@@ -98,11 +98,11 @@ void Shell::InitStandalone() {
           << "Observatory port specified was malformed. Will default to 8181";
     }
   }
-  // Start Paused
   settings.start_paused = command_line.HasSwitch(switches::kStartPaused);
-  // Set Checked Mode
   settings.enable_dart_checked_mode =
       command_line.HasSwitch(switches::kEnableCheckedMode);
+  settings.enable_background_compilation =
+      command_line.HasSwitch(switches::kEnableBackgroundCompilation);
   blink::SkySettings::Set(settings);
 
   Init();

sky/shell/switches.cc

@@ -11,6 +11,7 @@ namespace shell {
 namespace switches {
 
 const char kEnableCheckedMode[] = "enable-checked-mode";
+const char kEnableBackgroundCompilation[] = "enable-background-compilation";
 const char kFLX[] = "flx";
 const char kHelp[] = "help";
 const char kNonInteractive[] = "non-interactive";

sky/shell/switches.h

@@ -12,6 +12,7 @@ namespace shell {
 namespace switches {
 
 extern const char kEnableCheckedMode[];
+extern const char kEnableBackgroundCompilation[];
 extern const char kFLX[];
 extern const char kHelp[];
 extern const char kNonInteractive[];