Cleanup of the "empty-editor-focus" painting

Using the proper editor area (was cut off on the top). Not using
expensive alpha transparency anymore, but rather a slightly darker
color. Removing years-old rotten code that was in an '#if 0'.

src/plugins/coreplugin/editormanager/editorview.cpp

@@ -534,37 +534,11 @@ void SplitterOrView::paintEvent(QPaintEvent *)
     QPainter painter(this);
     painter.setRenderHint(QPainter::Antialiasing, true);
     painter.setPen(Qt::NoPen);
-    QColor shadeBrush(Qt::black);
-    shadeBrush.setAlpha(10);
-    painter.setBrush(shadeBrush);
+    painter.setBrush(palette().color(QPalette::Background).darker(107));
     const int r = 3;
-    painter.drawRoundedRect(rect().adjusted(r, r, -r, -r), r * 2, r * 2);
-
-#if 0
-    if (hasFocus()) {
-#ifdef Q_WS_MAC
-        // With QMacStyle, we have to draw our own focus rect, since I didn't find
-        // a way to draw the nice mac focus rect _inside_ this widget
-        if (qobject_cast<QMacStyle *>(style())) {
-            painter.setPen(Qt::DotLine);
-            painter.setBrush(Qt::NoBrush);
-            painter.setOpacity(0.75);
-            painter.drawRect(rect());
-        } else {
-#endif
-            QStyleOptionFocusRect option;
-            option.initFrom(this);
-            option.backgroundColor = palette().color(QPalette::Background);
-
-            // Some styles require a certain state flag in order to draw the focus rect
-            option.state |= QStyle::State_KeyboardFocusChange;
-
-            style()->drawPrimitive(QStyle::PE_FrameFocusRect, &option, &painter);
-#ifdef Q_WS_MAC
-        }
-#endif
-    }
-#endif
+    const QRect areaGlobal(view()->editorArea());
+    const QRect areaLocal(mapFromGlobal(areaGlobal.topLeft()), areaGlobal.size());
+    painter.drawRoundedRect(areaLocal.adjusted(r , r, -r, -r), r * 2, r * 2);
 }
 
 SplitterOrView *SplitterOrView::findFirstView()