Frameworks/base: Wall Werror in libs/hwui

Turn on -Wall -Werror in libs/hwui. Fix errors.

Change-Id: I74962d08c889712dacbd0d86d6760fc10802b6bd
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index 7eb9a32..8d529c6 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -244,7 +244,7 @@
 // Converts a number of kilo-bytes into bytes
 #define KB(s) s * 1024
 
-static DebugLevel readDebugLevel() {
+static inline DebugLevel readDebugLevel() {
     char property[PROPERTY_VALUE_MAX];
     if (property_get(PROPERTY_DEBUG, property, NULL) > 0) {
         return (DebugLevel) atoi(property);