Changed DisplayDevice.cpp to adhere to new getters in ProjectionSpace

Test: m -j
Bug: 15475032
Change-Id: I34e396a2a9e55bc3f2f59853204ed4e250185f19
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index 43a6bd5..9de578f 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -156,8 +156,8 @@
     // Return true if intent is supported by the display.
     bool hasRenderIntent(ui::RenderIntent intent) const;
 
-    const Rect& getBounds() const;
-    const Rect& bounds() const { return getBounds(); }
+    const Rect getBounds() const;
+    const Rect bounds() const { return getBounds(); }
 
     void setDisplayName(const std::string& displayName);
     const std::string& getDisplayName() const { return mDisplayName; }