Only suppress the sampling profiler on Mac/iOS when the engine is in debug...

Only suppress the sampling profiler on Mac/iOS when the engine is in debug mode. Makes the profiler available when using 'flutter run --profile' for iOS. (#2804)

Don't pass the --background-compilation vm flag as it has been enabled by default for quite awhile now.

sky/engine/core/script/dart_init.cc

@@ -83,7 +83,7 @@ static const char* kDartProfilingArgs[] = {
     // default profile period to 100Hz. This number is suitable for older
     // Raspberry Pi devices but quite low for current smartphones.
     "--profile_period=1000",
-#if (WTF_OS_IOS || WTF_OS_MACOSX)
+#if ((WTF_OS_IOS || WTF_OS_MACOSX) && !defined(NDEBUG))
     // On platforms where LLDB is the primary debugger, SIGPROF signals
     // overwhelm LLDB.
     "--no-profiler",
@@ -98,10 +98,6 @@ static const char* kDartPrecompilationArgs[] = {
     "--precompilation",
 };
 
-static const char* kDartBackgroundCompilationArgs[] = {
-  "--background_compilation",
-};
-
 static const char* kDartCheckedModeArgs[] = {
     "--enable_asserts",
     "--enable_type_checks",
@@ -514,8 +510,6 @@ void InitDartVM() {
 
   args.append(kDartProfilingArgs, arraysize(kDartProfilingArgs));
   args.append(kDartMirrorsArgs, arraysize(kDartMirrorsArgs));
-  args.append(kDartBackgroundCompilationArgs,
-              arraysize(kDartBackgroundCompilationArgs));
 
   if (IsRunningPrecompiledCode())
     args.append(kDartPrecompilationArgs, arraysize(kDartPrecompilationArgs));