Bug 1305202 - Use NullString() more and remove superfluous Truncates(). r=smaug

dom/ipc/Blob.cpp

@@ -3574,10 +3574,7 @@ BlobChild::SetMysteryBlobInfo(const nsString& aContentType, uint64_t aLength)
   MOZ_ASSERT(mBlobImpl);
   MOZ_ASSERT(mRemoteBlobImpl);
 
-  nsString voidString;
-  voidString.SetIsVoid(true);
-
-  mBlobImpl->SetLazyData(voidString, aContentType, aLength, INT64_MAX);
+  mBlobImpl->SetLazyData(NullString(), aContentType, aLength, INT64_MAX);
 
   NormalBlobConstructorParams params(aContentType,
                                      aLength,
@@ -4400,10 +4397,7 @@ BlobParent::RecvResolveMystery(const ResolveMysteryParams& aParams)
         return false;
       }
 
-      nsString voidString;
-      voidString.SetIsVoid(true);
-
-      mBlobImpl->SetLazyData(voidString,
+      mBlobImpl->SetLazyData(NullString(),
                              params.contentType(),
                              params.length(),
                              INT64_MAX);

dom/json/nsJSON.cpp

@@ -70,7 +70,6 @@ nsJSON::Encode(JS::Handle<JS::Value> aValue, JSContext* cx, uint8_t aArgc,
     return rv;
 
   if (aArgc == 0) {
-    aJSON.Truncate();
     aJSON.SetIsVoid(true);
     return NS_OK;
   }
@@ -83,7 +82,6 @@ nsJSON::Encode(JS::Handle<JS::Value> aValue, JSContext* cx, uint8_t aArgc,
     rv = NS_OK;
     // if we didn't consume anything, it's not JSON, so return null
     if (!writer.DidWrite()) {
-      aJSON.Truncate();
       aJSON.SetIsVoid(true);
     } else {
       writer.FlushBuffer();

dom/plugins/ipc/PluginMessageUtils.h

@@ -253,9 +253,7 @@ inline nsCString
 NullableString(const char* aString)
 {
     if (!aString) {
-        nsCString str;
-        str.SetIsVoid(true);
-        return str;
+        return NullCString();
     }
     return nsCString(aString);
 }

js/xpconnect/src/XPCConvert.cpp

@@ -640,7 +640,6 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
     {
         if (s.isNull() || s.isUndefined()) {
             nsACString* rs = *((nsACString**)d);
-            rs->Truncate();
             rs->SetIsVoid(true);
             return true;
         }

parser/html/nsHtml5TreeOperation.cpp

@@ -565,14 +565,12 @@ nsHtml5TreeOperation::AppendDoctypeToDocument(nsIAtom* aName,
   // Adapted from nsXMLContentSink
   // Create a new doctype node
   nsCOMPtr<nsIDOMDocumentType> docType;
-  nsAutoString voidString;
-  voidString.SetIsVoid(true);
   NS_NewDOMDocumentType(getter_AddRefs(docType),
                         aBuilder->GetNodeInfoManager(),
                         aName,
                         aPublicId,
                         aSystemId,
-                        voidString);
+                        NullString());
   NS_ASSERTION(docType, "Doctype creation failed.");
   nsCOMPtr<nsIContent> asContent = do_QueryInterface(docType);
   return AppendToDocument(asContent, aBuilder);

storage/Variant.h

@@ -357,7 +357,6 @@ public:
   NS_IMETHOD GetAsAUTF8String(nsACString &_str)
   {
     // Return a void string.
-    _str.Truncate(0);
     _str.SetIsVoid(true);
     return NS_OK;
   }
@@ -365,7 +364,6 @@ public:
   NS_IMETHOD GetAsAString(nsAString &_str)
   {
     // Return a void string.
-    _str.Truncate(0);
     _str.SetIsVoid(true);
     return NS_OK;
   }

storage/mozStorageArgValueArray.cpp

@@ -108,7 +108,6 @@ ArgValueArray::GetUTF8String(uint32_t aIndex,
   if (::sqlite3_value_type(mArgv[aIndex]) == SQLITE_NULL) {
     // NULL columns should have IsVoid set to distinguish them from an empty
     // string.
-    _value.Truncate(0);
     _value.SetIsVoid(true);
   }
   else {
@@ -127,7 +126,6 @@ ArgValueArray::GetString(uint32_t aIndex,
   if (::sqlite3_value_type(mArgv[aIndex]) == SQLITE_NULL) {
     // NULL columns should have IsVoid set to distinguish them from an empty
     // string.
-    _value.Truncate(0);
     _value.SetIsVoid(true);
   } else {
     _value.Assign(static_cast<const char16_t *>(::sqlite3_value_text16(mArgv[aIndex])),

storage/mozStorageStatement.cpp

@@ -772,7 +772,6 @@ Statement::GetUTF8String(uint32_t aIndex,
   if (type == mozIStorageStatement::VALUE_TYPE_NULL) {
     // NULL columns should have IsVoid set to distinguish them from the empty
     // string.
-    _value.Truncate(0);
     _value.SetIsVoid(true);
   }
   else {
@@ -795,7 +794,6 @@ Statement::GetString(uint32_t aIndex,
   if (type == mozIStorageStatement::VALUE_TYPE_NULL) {
     // NULL columns should have IsVoid set to distinguish them from the empty
     // string.
-    _value.Truncate(0);
     _value.SetIsVoid(true);
   } else {
     const char16_t *value =

toolkit/components/places/nsNavBookmarks.cpp

@@ -799,11 +799,9 @@ nsNavBookmarks::InsertSeparator(int64_t aParent,
 
   *aNewItemId = -1;
   // Set a NULL title rather than an empty string.
-  nsCString voidString;
-  voidString.SetIsVoid(true);
   nsAutoCString guid(aGUID);
   PRTime dateAdded = RoundedPRNow();
-  rv = InsertBookmarkInDB(-1, SEPARATOR, aParent, index, voidString, dateAdded,
+  rv = InsertBookmarkInDB(-1, SEPARATOR, aParent, index, NullCString(), dateAdded,
                           0, folderGuid, grandParentId, nullptr, aSource,
                           aNewItemId, guid);
   NS_ENSURE_SUCCESS(rv, rv);
@@ -814,7 +812,7 @@ nsNavBookmarks::InsertSeparator(int64_t aParent,
   NOTIFY_OBSERVERS(mCanNotify, mCacheObservers, mObservers,
                    nsINavBookmarkObserver,
                    OnItemAdded(*aNewItemId, aParent, index, TYPE_SEPARATOR,
-                               nullptr, voidString, dateAdded, guid, folderGuid,
+                               nullptr, NullCString(), dateAdded, guid, folderGuid,
                                aSource));
 
   return NS_OK;

xpcom/ds/nsVariant.cpp

@@ -766,7 +766,6 @@ nsDiscriminatedUnion::ToString(nsACString& aOutString) const
 
     case nsIDataType::VTYPE_VOID:
     case nsIDataType::VTYPE_EMPTY:
-      aOutString.Truncate();
       aOutString.SetIsVoid(true);
       return NS_OK;