IOS macros have not been namespaced yet.

Author: chinmaygarde

impeller/renderer/backend/metal/allocator_mtl.mm

@@ -32,15 +32,15 @@
 static MTLResourceOptions ToMTLResourceOptions(StorageMode type) {
   switch (type) {
     case StorageMode::kHostVisible:
-#if FML_OS_IOS
+#if OS_IOS
       return MTLResourceStorageModeShared;
 #else
       return MTLResourceStorageModeManaged;
 #endif
     case StorageMode::kDevicePrivate:
       return MTLResourceStorageModePrivate;
     case StorageMode::kDeviceTransient:
-#if FML_OS_IOS
+#if OS_IOS
       if (@available(iOS 10.0, *)) {
         return MTLResourceStorageModeMemoryless;
       } else {
@@ -57,15 +57,15 @@ static MTLResourceOptions ToMTLResourceOptions(StorageMode type) {
 static MTLStorageMode ToMTLStorageMode(StorageMode mode) {
   switch (mode) {
     case StorageMode::kHostVisible:
-#if FML_OS_IOS
+#if OS_IOS
       return MTLStorageModeShared;
 #else
       return MTLStorageModeManaged;
 #endif
     case StorageMode::kDevicePrivate:
       return MTLStorageModePrivate;
     case StorageMode::kDeviceTransient:
-#if FML_OS_IOS
+#if OS_IOS
       if (@available(iOS 10.0, *)) {
         return MTLStorageModeMemoryless;
       } else {