Frameworks/base: Wall Werror in libs/hwui

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

Change-Id: I74962d08c889712dacbd0d86d6760fc10802b6bd
diff --git a/libs/hwui/renderthread/RenderProxy.cpp b/libs/hwui/renderthread/RenderProxy.cpp
index 047819d..c6ea82b 100644
--- a/libs/hwui/renderthread/RenderProxy.cpp
+++ b/libs/hwui/renderthread/RenderProxy.cpp
@@ -349,8 +349,12 @@
     return NULL;
 }
 
+template <typename T>
+void UNUSED(T t) {}
+
 void RenderProxy::fence() {
     SETUP_TASK(fence);
+    UNUSED(args);
     postAndWait(task);
 }