Timeline: avoid rebuilding of text nodes

Using an array of strings as model has the unfortunate effect that all
text nodes resulting from it are rebuilt whenever anything in the
array changes. Using a number as model only triggers a rebuild of
everything when the number changes.

Change-Id: I8a762e78eb75b282f46641a6cba6eff43c8ebfd5
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

src/libs/timeline/qml/SelectionRangeDetails.qml

@@ -144,17 +144,20 @@ Item {
             columns: 2
 
             Repeater {
-                model: [
+                id: details
+                property var contents: [
                     qsTr("Start") + ":",
                     detailedPrintTime(startTime),
-                    showDuration ? (qsTr("End") + ":") : "",
-                    showDuration ? detailedPrintTime(endTime) : "",
-                    showDuration ? (qsTr("Duration") + ":") : "",
-                    showDuration ? detailedPrintTime(duration) : ""
+                    (qsTr("End") + ":"),
+                    detailedPrintTime(endTime),
+                    (qsTr("Duration") + ":"),
+                    detailedPrintTime(duration)
                 ]
+
+                model: showDuration ? 6 : 2
                 Detail {
                     isLabel: index % 2 === 0
-                    text: modelData
+                    text: details.contents[index]
                 }
             }
         }