Manifest, pro file and CMake editor can have fixed mime type set

Can be set directly from the document constructor, no need to do that
later.

Change-Id: I4326757e1b1cb1e48c157c4b330ccb2abb8f3b1f
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/android/androidmanifestdocument.cpp

@@ -44,6 +44,7 @@ AndroidManifestDocument::AndroidManifestDocument(AndroidManifestEditorWidget *ed
     : TextEditor::BaseTextDocument(),
       m_editorWidget(editorWidget)
 {
+    setMimeType(QLatin1String(Constants::ANDROID_MANIFEST_MIME_TYPE));
 }
 
 bool AndroidManifestDocument::save(QString *errorString, const QString &fileName, bool autoSave)