Docs and comments

Author: GaryQian

packages/in_app_purchase/in_app_purchase_android/android/src/main/java/io/flutter/plugins/inapppurchase/MethodCallHandlerImpl.java

@@ -314,7 +314,8 @@ private void queryPurchasesAsync(String skuType, MethodChannel.Result result) {
             public void onQueryPurchasesResponse(
                 BillingResult billingResult, List<Purchase> purchasesList) {
               final Map<String, Object> serialized = new HashMap<>();
-              // The response code is no longer passed, as part of billing 4.1.0, so we pass OK here.
+              // The response code is no longer passed, as part of billing 4.0, so we pass OK here
+              // as success is implied by calling this callback.
               serialized.put("responseCode", BillingClient.BillingResponseCode.OK);
               serialized.put("billingResult", Translator.fromBillingResult(billingResult));
               serialized.put(

packages/in_app_purchase/in_app_purchase_android/android/src/main/java/io/flutter/plugins/inapppurchase/Translator.java

@@ -61,6 +61,10 @@ static HashMap<String, Object> fromPurchase(Purchase purchase) {
     info.put("purchaseTime", purchase.getPurchaseTime());
     info.put("purchaseToken", purchase.getPurchaseToken());
     info.put("signature", purchase.getSignature());
+    // TODO(garyq): Remove deprecated `sku`.
+    // `sku` was deprecated in billion 4.0, but we cannot directly remove it from our
+    // API instantly. Thus, for backwards compatibility, we pass the first sku here
+    // and include the rest of the list under `skus`.
     if (!skus.isEmpty()) {
       info.put("sku", skus.get(0));
     }
@@ -86,6 +90,10 @@ static HashMap<String, Object> fromPurchaseHistoryRecord(
     info.put("purchaseTime", purchaseHistoryRecord.getPurchaseTime());
     info.put("purchaseToken", purchaseHistoryRecord.getPurchaseToken());
     info.put("signature", purchaseHistoryRecord.getSignature());
+    // TODO(garyq): Remove deprecated `sku`.
+    // `sku` was deprecated in billion 4.0, but we cannot directly remove it from our
+    // API instantly. Thus, for backwards compatibility, we pass the first sku here
+    // and include the rest of the list under `skus`.
     if (!skus.isEmpty()) {
       info.put("sku", skus.get(0));
     }