Allow use of assets for data in the dictionary content provider.

This update is necessary to allow dictionary content providers to use
assets, which are part of their apk, as data to pass to the keyboard.
Using plain file descriptors doesn't allow for sections of files to
be correctly used.

Change-Id: Ia94c26d6387bce61c73d38f5c2821f20e50e54d4

java/src/com/android/inputmethod/latin/BinaryDictionaryFileDumper.java

@@ -18,6 +18,7 @@ package com.android.inputmethod.latin;
 
 import android.content.ContentResolver;
 import android.content.Context;
+import android.content.res.AssetFileDescriptor;
 import android.net.Uri;
 import android.text.TextUtils;
 
@@ -96,9 +97,9 @@ public class BinaryDictionaryFileDumper {
         // file.
         final ContentResolver resolver = context.getContentResolver();
         final Uri dictionaryPackUri = getProviderUri(locale);
-        final InputStream stream = resolver.openInputStream(dictionaryPackUri);
-        if (null == stream) return null;
-        return copyFileTo(stream, getCacheFileNameForLocale(locale, context));
+        final AssetFileDescriptor afd = resolver.openAssetFileDescriptor(dictionaryPackUri, "r");
+        if (null == afd) return null;
+        return copyFileTo(afd.createInputStream(), getCacheFileNameForLocale(locale, context));
     }
 
     /**
@@ -128,6 +129,8 @@ public class BinaryDictionaryFileDumper {
     /**
      * Copies the data in an input stream to a target file, creating the file if necessary and
      * overwriting it if it already exists.
+     * @param input the stream to be copied.
+     * @param outputFileName the name of a file to copy the data to. It is created if necessary.
      */
     private static String copyFileTo(final InputStream input, final String outputFileName)
             throws FileNotFoundException, IOException {