Properly clear textures for Hardware Bitmaps

Test: manual  (Description in the bug)
bug:34858530
Change-Id: I13eb89077c43ca28436509a7af5b7c11374446c4
diff --git a/libs/hwui/debug/nullegl.cpp b/libs/hwui/debug/nullegl.cpp
index 1ce180dd..2ae71df 100644
--- a/libs/hwui/debug/nullegl.cpp
+++ b/libs/hwui/debug/nullegl.cpp
@@ -22,6 +22,7 @@
 #include <string.h>
 
 static EGLDisplay gDisplay = (EGLDisplay) 1;
+static EGLSyncKHR gFence = (EGLSyncKHR) 1;
 
 typedef struct {
     EGLSurface surface;
@@ -159,6 +160,18 @@
     return (EGLImageKHR) malloc(sizeof(EGLImageKHR));
 }
 
+EGLSyncKHR eglCreateSyncKHR(EGLDisplay dpy, EGLenum type, const EGLint *attrib_list) {
+    return gFence;
+}
+
+EGLBoolean eglDestroySyncKHR(EGLDisplay dpy, EGLSyncKHR sync) {
+    return EGL_TRUE;
+}
+
+EGLint eglClientWaitSyncKHR(EGLDisplay dpy, EGLSyncKHR sync, EGLint flags, EGLTimeKHR timeout) {
+    return EGL_CONDITION_SATISFIED_KHR;
+}
+
 EGLBoolean eglDestroyImageKHR(EGLDisplay dpy, EGLImageKHR image) {
     free(image);
     return EGL_TRUE;