Core: Do not warn about big file that is already open

This is especially annoying during debug, when each step pops this
warning.

Change-Id: Id309c881f6b3062bc140740fe22b5c90cfddd08c
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/editormanager/editormanager.cpp

@@ -604,6 +604,9 @@ IEditor *EditorManagerPrivate::openEditor(EditorView *view, const QString &fileN
         }
     }
 
+    if (skipOpeningBigTextFile(fileName))
+        return nullptr;
+
     IEditor *editor = 0;
     auto overrideCursor = Utils::OverrideCursor(QCursor(Qt::WaitCursor));
 
@@ -2618,9 +2621,6 @@ EditorManager::ExternalEditorList
 IEditor *EditorManager::openEditor(const QString &fileName, Id editorId,
                                    OpenEditorFlags flags, bool *newEditor)
 {
-    if (EditorManagerPrivate::skipOpeningBigTextFile(fileName))
-        return 0;
-
     if (flags & EditorManager::OpenInOtherSplit)
         EditorManager::gotoOtherSplit();
 
@@ -2631,9 +2631,6 @@ IEditor *EditorManager::openEditor(const QString &fileName, Id editorId,
 IEditor *EditorManager::openEditorAt(const QString &fileName, int line, int column,
                                      Id editorId, OpenEditorFlags flags, bool *newEditor)
 {
-    if (EditorManagerPrivate::skipOpeningBigTextFile(fileName))
-        return 0;
-
     if (flags & EditorManager::OpenInOtherSplit)
         EditorManager::gotoOtherSplit();