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

android_webview/native/aw_assets.cc

+// 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.
+
+#include <jni.h>
+
+#include "android_webview/native/aw_assets.h"
+
+#include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
+#include "base/android/scoped_java_ref.h"
+#include "jni/AwAssets_jni.h"
+
+namespace android_webview {
+namespace AwAssets {
+
+bool OpenAsset(const std::string& filename,
+               int* fd,
+               int64* offset,
+               int64* size) {
+  JNIEnv* env = base::android::AttachCurrentThread();
+  ScopedJavaLocalRef<jlongArray> jarr = Java_AwAssets_openAsset(
+      env,
+      base::android::GetApplicationContext(),
+      base::android::ConvertUTF8ToJavaString(env, filename).Release());
+  std::vector<long> results;
+  base::android::JavaLongArrayToLongVector(env, jarr.obj(), &results);
+  DCHECK_EQ(3U, results.size());
+  *fd = static_cast<int>(results[0]);
+  *offset = results[1];
+  *size = results[2];
+  return *fd != -1;
+}
+
+}  // namespace AwAssets
+
+bool RegisterAwAssets(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}  // namespace android_webview