Fix possible infinite loop when purging textures.

Change-Id: Ib05b398ae03e734da2dab0496df416fed4570b1c
diff --git a/libs/hwui/Texture.h b/libs/hwui/Texture.h
index 90f548b..817f143 100644
--- a/libs/hwui/Texture.h
+++ b/libs/hwui/Texture.h
@@ -28,6 +28,7 @@
 struct Texture {
     Texture() {
         cleanup = false;
+        bitmapSize = 0;
     }
 
     /**
@@ -54,6 +55,10 @@
      * Indicates whether this texture should be cleaned up after use.
      */
     bool cleanup;
+    /**
+     * Optional, size of the original bitmap.
+     */
+    uint32_t bitmapSize;
 }; // struct Texture
 
 class AutoTexture {