Drop Phase2Data constructors

Summary:
We initialize all fields of Phase2Data at once, so the constructors seem
to be redundant.

Reviewers: #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D18207

scene.cpp

@@ -232,7 +232,7 @@ void Scene::paintGenericScreen(int orig_mask, ScreenPaintData)
         if (!w->isPaintingEnabled()) {
             continue;
         }
-        phase2.append(Phase2Data(w, infiniteRegion(), data.clip, data.mask, data.quads));
+        phase2.append({w, infiniteRegion(), data.clip, data.mask, data.quads});
     }
 
     foreach (const Phase2Data & d, phase2) {

scene.h

@@ -228,16 +228,10 @@ protected:
     void updateTimeDiff();
     // saved data for 2nd pass of optimized screen painting
     struct Phase2Data {
-        Phase2Data(Window* w, QRegion r, QRegion c, int m, const WindowQuadList& q)
-            : window(w), region(r), clip(c), mask(m), quads(q) {}
-        Phase2Data()  {
-            window = 0;
-            mask = 0;
-        }
-        Window* window;
+        Window *window = nullptr;
         QRegion region;
         QRegion clip;
-        int mask;
+        int mask = 0;
         WindowQuadList quads;
     };
     // The region which actually has been painted by paintScreen() and should be