Implement the new Photo picker, part two.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/DecoderServiceHost.java

Index: chrome/android/java/src/org/chromium/chrome/browser/photo_picker/DecoderServiceHost.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/DecoderServiceHost.java b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/DecoderServiceHost.java
new file mode 100644
index 0000000000000000000000000000000000000000..1fa1640a51ed7e03058b7e6900a2c4aeb916877b
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/DecoderServiceHost.java
@@ -0,0 +1,99 @@
+// Copyright 2016 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.chrome.browser.photo_picker;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+
+/**
+ * A class to communicate with the decoder service.
+ */
+public class DecoderServiceHost {
+    /**
+     * Interface for notifying clients of the service being ready.
+     */
+    public interface ServiceReadyCallback {
+        /**
+         * A function to define to receive a notification once the service is up and running.
+         */
+        void serviceReady();
+    }
+
+    /**
+     * An interface notifying clients when an image has finished decoding.
+     */
+    public interface ImageDecodedCallback {
+        /**
+         * A function to define to receive a notification that an image has been decoded.
+         * @param filePath The file path for the newly decoded image.
+         * @param bitmap The results of the decoding (or placeholder image, if failed).
+         */
+        void imageDecodedCallback(String filePath, Bitmap bitmap);
+    }
+
+    // The callback the client wants us to use to report back when the service is ready.
+    private ServiceReadyCallback mCallback;
+
+    /**
+     * The DecoderServiceHost constructor.
+     * @param callback The callback to use when communicating back to the client.
+     */
+    public DecoderServiceHost(ServiceReadyCallback callback) {
+        mCallback = callback;
+    }
+
+    /**
+     * Initiate binding with the decoder service.
+     * @param context The context to use.
+     */
+    public void bind(Context context) {
+        mCallback.serviceReady();
+    }
+
+    /**
+     * Unbind from the decoder service.
+     * @param context The context to use.
+     */
+    public void unbind(Context context) {
+        // TODO(finnur): Implement.
+    }
+
+    /**
+     * Accepts a request to decode a single image.
+     * @param filePath The path to the file to decode.
+     * @param width The requested width of the resulting bitmap.
+     * @param callback The callback to use to communicate the decoding results.
+     */
+    public void decodeImage(String filePath, int width, ImageDecodedCallback callback) {
+        // TODO(finnur): Queue up and actually decode the image requested.
+        callback.imageDecodedCallback(filePath, createPlaceholderBitmap(width, width));
+    }
+
+    /**
+     * Cancels a request to decode an image (if it hasn't already been dispatched).
+     * @param filePath
+     */
+    public void cancelDecodeImage(String filePath) {
+        // TODO(finnur): Implement.
+    }
+
+    /**
+     * Creates a placeholder bitmap, used when the server failed to decode the image.
+     * @param width The requested width of the resulting bitmap.
+     * @param height The requested height of the resulting bitmap.
+     * @return Placeholder bitmap.
+     */
+    private Bitmap createPlaceholderBitmap(int width, int height) {
+        Bitmap placeholder = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        Canvas canvas = new Canvas(placeholder);
+        Paint paint = new Paint();
+        paint.setColor(Color.GRAY);
+        canvas.drawRect(0, 0, (float) width, (float) height, paint);
+        return placeholder;
+    }
+}