Correctly detect the wrong Z value for the light

b/17221975

Change-Id: I2b46da95ad12ca5260d7fe9514a75558b6b6393b
diff --git a/libs/hwui/utils/MathUtils.h b/libs/hwui/utils/MathUtils.h
index 00448b8..d89859b 100644
--- a/libs/hwui/utils/MathUtils.h
+++ b/libs/hwui/utils/MathUtils.h
@@ -76,6 +76,11 @@
         return a < b ? a : b;
     }
 
+    template<typename T>
+    static inline T clamp(T a, T minValue, T maxValue) {
+        return min(max(a, minValue), maxValue);
+    }
+
     inline static float lerp(float v1, float v2, float t) {
         return v1 + ((v2 - v1) * t);
     }