Ensure glActiveTexture is cleaned up correctly on functor resume

Change-Id: I103d7d63b17289d599c2c08dcc442cfba9b8e51d
diff --git a/libs/hwui/Caches.cpp b/libs/hwui/Caches.cpp
index 6de8c8c..6ac637e 100644
--- a/libs/hwui/Caches.cpp
+++ b/libs/hwui/Caches.cpp
@@ -495,6 +495,10 @@
     }
 }
 
+void Caches::resetActiveTexture() {
+    mTextureUnit = -1;
+}
+
 void Caches::bindTexture(GLuint texture) {
     if (mBoundTextures[mTextureUnit] != texture) {
         glBindTexture(GL_TEXTURE_2D, texture);