Added a isLocalFileUrlOrPath(Uri) method to remove manual checks

Also replaced the manual checks with a call to this method

demo/src/main/java/com/google/android/exoplayer/demo/PlayerActivity.java

@@ -293,15 +293,12 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
     }
   }
 
-  private boolean uriIsLocalFile(Uri uri) {
-    return URI_FILE_SCHEME.equals(uri.getScheme()) || TextUtils.isEmpty(uri.getScheme());
-  }
-
   @TargetApi(23)
   private boolean requiresPermission(Uri uri) {
-    return Util.SDK_INT >= 23 && uriIsLocalFile(uri)
+    return Util.SDK_INT >= 23
+        && Util.isLocalFileUri(uri)
         && checkSelfPermission(permission.READ_EXTERNAL_STORAGE)
-        != PackageManager.PERMISSION_GRANTED;
+            != PackageManager.PERMISSION_GRANTED;
   }
 
   // Internal methods

library/src/main/java/com/google/android/exoplayer/upstream/DefaultUriDataSource.java

@@ -16,9 +16,9 @@
 package com.google.android.exoplayer.upstream;
 
 import com.google.android.exoplayer.util.Assertions;
+import com.google.android.exoplayer.util.Util;
 
 import android.content.Context;
-import android.text.TextUtils;
 
 import java.io.IOException;
 
@@ -36,7 +36,6 @@ import java.io.IOException;
  */
 public final class DefaultUriDataSource implements UriDataSource {
 
-  private static final String SCHEME_FILE = "file";
   private static final String SCHEME_ASSET = "asset";
   private static final String SCHEME_CONTENT = "content";
 
@@ -119,7 +118,7 @@ public final class DefaultUriDataSource implements UriDataSource {
     Assertions.checkState(dataSource == null);
     // Choose the correct source for the scheme.
     String scheme = dataSpec.uri.getScheme();
-    if (SCHEME_FILE.equals(scheme) || TextUtils.isEmpty(scheme)) {
+    if (Util.isLocalFileUri(dataSpec.uri)) {
       if (dataSpec.uri.getPath().startsWith("/android_asset/")) {
         dataSource = assetDataSource;
       } else {

library/src/main/java/com/google/android/exoplayer/util/Util.java

@@ -25,6 +25,7 @@ import android.content.Context;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
+import android.net.Uri;
 import android.os.Build;
 import android.text.TextUtils;
 
@@ -106,12 +107,13 @@ public final class Util {
   }
 
   /**
-   * Returns true if the URL points to a file on the local device
+   * Returns true if the URI is a path to a local file or a reference to a local file.
    *
-   * @param url The URL to test
+   * @param uri The uri to test.
    */
-  public static boolean isUrlLocalFile(URL url) {
-    return url.getProtocol().equals("file");
+  public static boolean isLocalFileUri(Uri uri) {
+    String scheme = uri.getScheme();
+    return TextUtils.isEmpty(scheme) || scheme.equals("file");
   }
 
   /**