Allow controlling the SDR white point

Test: this
Change-Id: I9ee059afd73ca0850e41072c068c9effe8362382
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index c8f6b3b..85a0f4a 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -249,6 +249,8 @@
 
     static int defaultRenderAhead;
 
+    static float defaultSdrWhitePoint;
+
 private:
     static ProfileType sProfileType;
     static bool sDisableProfileBars;