Refactor SurfaceFlinger::rebuildLayerStacks

Reduce indentation with early return

Change-Id: Ic3a16bf45a0c1792b0fcbd5d9d1cd9f1e239ae32
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 2781e8c..c8b4081 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1549,46 +1549,49 @@
     ALOGV("rebuildLayerStacks");
 
     // rebuild the visible layer list per screen
-    if (CC_UNLIKELY(mVisibleRegionsDirty)) {
-        ATRACE_CALL();
-        mVisibleRegionsDirty = false;
-        invalidateHwcGeometry();
-
-        for (size_t dpy=0 ; dpy<mDisplays.size() ; dpy++) {
-            Region opaqueRegion;
-            Region dirtyRegion;
-            Vector<sp<Layer>> layersSortedByZ;
-            const sp<DisplayDevice>& displayDevice(mDisplays[dpy]);
-            const Transform& tr(displayDevice->getTransform());
-            const Rect bounds(displayDevice->getBounds());
-            if (displayDevice->isDisplayOn()) {
-                computeVisibleRegions(
-                        displayDevice->getLayerStack(), dirtyRegion,
-                        opaqueRegion);
-
-                mDrawingState.traverseInZOrder([&](Layer* layer) {
-                    if (layer->getLayerStack() == displayDevice->getLayerStack()) {
-                        Region drawRegion(tr.transform(
-                                layer->visibleNonTransparentRegion));
-                        drawRegion.andSelf(bounds);
-                        if (!drawRegion.isEmpty()) {
-                            layersSortedByZ.add(layer);
-                        } else {
-                            // Clear out the HWC layer if this layer was
-                            // previously visible, but no longer is
-                            layer->setHwcLayer(displayDevice->getHwcDisplayId(),
-                                    nullptr);
-                        }
-                    }
-                });
-            }
-            displayDevice->setVisibleLayersSortedByZ(layersSortedByZ);
-            displayDevice->undefinedRegion.set(bounds);
-            displayDevice->undefinedRegion.subtractSelf(
-                    tr.transform(opaqueRegion));
-            displayDevice->dirtyRegion.orSelf(dirtyRegion);
-        }
+    if (CC_LIKELY(mVisibleRegionsDirty)) {
+        return;
     }
+
+    ATRACE_NAME("rebuildLayerStacks VR Dirty");
+    mVisibleRegionsDirty = false;
+    invalidateHwcGeometry();
+
+    for (size_t dpy=0 ; dpy<mDisplays.size() ; dpy++) {
+        Region opaqueRegion;
+        Region dirtyRegion;
+        Vector<sp<Layer>> layersSortedByZ;
+        const sp<DisplayDevice>& displayDevice(mDisplays[dpy]);
+        const Transform& tr(displayDevice->getTransform());
+        const Rect bounds(displayDevice->getBounds());
+        if (displayDevice->isDisplayOn()) {
+            computeVisibleRegions(
+                    displayDevice->getLayerStack(), dirtyRegion,
+                    opaqueRegion);
+
+            mDrawingState.traverseInZOrder([&](Layer* layer) {
+                if (layer->getLayerStack() == displayDevice->getLayerStack()) {
+                    Region drawRegion(tr.transform(
+                            layer->visibleNonTransparentRegion));
+                    drawRegion.andSelf(bounds);
+                    if (!drawRegion.isEmpty()) {
+                        layersSortedByZ.add(layer);
+                    } else {
+                        // Clear out the HWC layer if this layer was
+                        // previously visible, but no longer is
+                        layer->setHwcLayer(displayDevice->getHwcDisplayId(),
+                                nullptr);
+                    }
+                }
+            });
+        }
+        displayDevice->setVisibleLayersSortedByZ(layersSortedByZ);
+        displayDevice->undefinedRegion.set(bounds);
+        displayDevice->undefinedRegion.subtractSelf(
+                tr.transform(opaqueRegion));
+        displayDevice->dirtyRegion.orSelf(dirtyRegion);
+    }
+
 }
 
 void SurfaceFlinger::setUpHWComposer() {