[android_webview] Introduce AwAssets to reference assets inside the apk.

android_webview/java/src/org/chromium/android_webview/AwAssets.java

Index: android_webview/java/src/org/chromium/android_webview/AwAssets.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwAssets.java b/android_webview/java/src/org/chromium/android_webview/AwAssets.java
new file mode 100644
index 0000000000000000000000000000000000000000..97e292ff7a37ff0be2f9088c6ff60b1e9ebaf755
--- /dev/null
+++ b/android_webview/java/src/org/chromium/android_webview/AwAssets.java
@@ -0,0 +1,38 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.android_webview;
+
+import android.content.Context;
+import android.content.res.AssetFileDescriptor;
+import android.content.res.AssetManager;
+import android.util.Log;
+
+import org.chromium.base.CalledByNative;
+import org.chromium.base.JNINamespace;
+
+import java.io.IOException;
+
+/**
+ * A utility class to retrieve references to uncompressed assets insides the apk. A reference is
+ * defined as tuple (file descriptor, offset, size) enabling direct mapping without deflation.
+ */
+@JNINamespace("android_webview")
+public class AwAssets {
+    private static final String LOGTAG = "AwAssets";
+
+    @CalledByNative
+    public static long[] openAsset(Context context, String fileName) {
+        try {
+            AssetManager manager = context.getAssets();
+            AssetFileDescriptor afd = manager.openFd(fileName);
+            return new long[] { afd.getParcelFileDescriptor().detachFd(),
+                                afd.getStartOffset(),
+                                afd.getLength() };
+        } catch (IOException e) {
+            Log.e(LOGTAG, "Error while loading asset " + fileName + ": " + e.getMessage());
+            return new long[] {-1, -1, -1};
+        }
+    }
+}