Fix flickering when layers resize in-place

bug:27248275
Change-Id: Ia11c93ebc1097f3735071204b6f14ca079bb9fc4
diff --git a/libs/hwui/debug/nullgles.cpp b/libs/hwui/debug/nullgles.cpp
index ffb0649..8689f98 100644
--- a/libs/hwui/debug/nullgles.cpp
+++ b/libs/hwui/debug/nullgles.cpp
@@ -133,6 +133,15 @@
     }
 }
 
+GLenum glCheckFramebufferStatus(GLenum target) {
+    switch (target) {
+    case GL_FRAMEBUFFER:
+        return GL_FRAMEBUFFER_COMPLETE;
+    default:
+        return 0; // error case
+    }
+}
+
 const char* getString(GLenum name) {
     switch (name) {
     case GL_VENDOR: