Implement OmxJpegImageDecoder.

Add StreamSource, which wraps a SkStream to a DataSource.
Add SkOmxPixelRef, which holds a MediaBuffer.
Test OmxJpegImageDecoder by a Jpeg decoder bench.
diff --git a/media/tests/omxjpegdecoder/SkOmxPixelRef.cpp b/media/tests/omxjpegdecoder/SkOmxPixelRef.cpp
new file mode 100644
index 0000000..3acc0ee
--- /dev/null
+++ b/media/tests/omxjpegdecoder/SkOmxPixelRef.cpp
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <media/stagefright/MediaDebug.h>
+#include <SkBitmap.h>
+
+#include "SkOmxPixelRef.h"
+
+using namespace android;
+
+SkOmxPixelRef::SkOmxPixelRef(SkColorTable* ctable, MediaBuffer* buffer,
+        sp<OMXCodec> decoder)  {
+    mBuffer = buffer;
+    mDecoder = decoder;
+    mSize = buffer->size();
+    mCTable = ctable;
+    SkSafeRef(mCTable);
+}
+
+SkOmxPixelRef::~SkOmxPixelRef() {
+    mBuffer->release();
+    CHECK_EQ(mDecoder->stop(), OK);
+    SkSafeUnref(mCTable);
+}
+
+void* SkOmxPixelRef::onLockPixels(SkColorTable** ct) {
+    *ct = mCTable;
+    return mBuffer->data();
+}
+
+void SkOmxPixelRef::onUnlockPixels() {
+    // nothing to do
+}