Continue error check improvements and write some docs.

Change-Id: I345b08490da21d9ee715ff1ddc80c1a816b579f4
diff --git a/graphics/java/android/renderscript/FileA3D.java b/graphics/java/android/renderscript/FileA3D.java
index fc74fc4..af85d8e 100644
--- a/graphics/java/android/renderscript/FileA3D.java
+++ b/graphics/java/android/renderscript/FileA3D.java
@@ -149,7 +149,7 @@
     }
 
     private void initEntries() {
-        int numFileEntries = mRS.nFileA3DGetNumIndexEntries(mID);
+        int numFileEntries = mRS.nFileA3DGetNumIndexEntries(getID());
         if(numFileEntries <= 0) {
             return;
         }
@@ -158,10 +158,10 @@
         int[] ids = new int[numFileEntries];
         String[] names = new String[numFileEntries];
 
-        mRS.nFileA3DGetIndexEntries(mID, numFileEntries, ids, names);
+        mRS.nFileA3DGetIndexEntries(getID(), numFileEntries, ids, names);
 
         for(int i = 0; i < numFileEntries; i ++) {
-            mFileEntries[i] = new IndexEntry(mRS, i, mID, names[i], ClassID.toClassID(ids[i]));
+            mFileEntries[i] = new IndexEntry(mRS, i, getID(), names[i], ClassID.toClassID(ids[i]));
         }
     }