[android_webview] Don't block the IO thread when reading from an InputStream.

android_webview/native/input_stream_impl.h

+// Copyright (c) 2012 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.
+
+#ifndef ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_H_
+#define ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_H_
+
+#include "android_webview/browser/input_stream.h"
+#include "base/android/scoped_java_ref.h"
+#include "base/compiler_specific.h"
+
+namespace net {
+class IOBuffer;
+}
+
+namespace android_webview {
+
+class InputStreamImpl : public InputStream {
+ public:
+  // Maximum size of |buffer_|.
+  static const int kBufferSize;
+
+  static const InputStreamImpl* FromInputStream(
+      const InputStream* input_stream);
+
+  // |stream| should be an instance of the InputStream Java class.
+  // |stream| can't be null.
+  InputStreamImpl(const base::android::JavaRef<jobject>& stream);
+  virtual ~InputStreamImpl();
+
+  // Gets the underlying Java object. Guaranteed non-NULL.
+  const jobject jobj() const { return jobject_.obj(); }
+
+  // InputStream implementation.
+  virtual bool BytesAvailable(int* bytes_available) const OVERRIDE;
+  virtual bool Skip(int64_t n, int64_t* bytes_skipped) OVERRIDE;
+  virtual bool Read(net::IOBuffer* dest, int length, int* bytes_read) OVERRIDE;
+ protected:
+  // Parameterless constructor exposed for testing.
+  InputStreamImpl();
+
+ private:
+  base::android::ScopedJavaGlobalRef<jobject> jobject_;
+  base::android::ScopedJavaGlobalRef<jbyteArray> buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(InputStreamImpl);
+};
+
+bool RegisterInputStream(JNIEnv* env);
+
+} // namespace android_webview
+
+#endif //  ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_H_