Turn the utility process image decoder into a Mojo service.

components/image_decoder/image_decoder_impl.cc

+// Copyright 2015 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 "components/image_decoder/image_decoder_impl.h"
+
+#include <string.h>
+
+#include "base/logging.h"
+#include "content/public/child/image_decoder_utils.h"
+#include "ipc/ipc_channel.h"
+#include "skia/ext/image_operations.h"
+#include "skia/public/type_converters.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "ui/gfx/codec/jpeg_codec.h"
+#include "ui/gfx/geometry/size.h"
+
+namespace image_decoder {
+
+namespace {
+// TODO(amistry): Replace with more correct value.

[Sam McNally, 2015/05/06 06:41:39]

According to
https://code.google.com/p/chromium/codesearch/#chromium/src/content/app/mojo/...,
this should be the correct value.

[Anand Mistry (off Chromium), 2015/05/06 07:14:23]

Thanks.

+int64_t kMaxMessageSize = IPC::Channel::kMaximumMessageSize;
+}
+
+ImageDecoderImpl::ImageDecoderImpl(int64_t max_message_size)
+    : max_message_size_(max_message_size), binding_(this) {
+}
+
+ImageDecoderImpl::ImageDecoderImpl(mojo::InterfaceRequest<ImageDecoder> request)
+    : max_message_size_(kMaxMessageSize), binding_(this, request.Pass()) {
+}
+
+ImageDecoderImpl::~ImageDecoderImpl() {
+}
+
+void ImageDecoderImpl::DecodeImage(
+    mojo::Array<uint8_t> encoded_data,
+    ImageCodec codec,
+    bool shrink_to_fit,
+    const mojo::Callback<void(skia::BitmapPtr)>& callback) {
+  if (encoded_data.size() == 0) {
+    callback.Run(nullptr);
+    return;
+  }
+
+  SkBitmap decoded_image;
+  if (codec == IMAGE_CODEC_ROBUST_JPEG) {
+    // Our robust jpeg decoding is using IJG libjpeg.
+    if (gfx::JPEGCodec::JpegLibraryVariant() == gfx::JPEGCodec::IJG_LIBJPEG &&
+        encoded_data.size()) {
+      scoped_ptr<SkBitmap> decoded_jpeg(
+          gfx::JPEGCodec::Decode(&encoded_data[0], encoded_data.size()));
+      if (decoded_jpeg.get() && !decoded_jpeg->empty())
+        decoded_image = *decoded_jpeg;
+    }
+  } else {
+    decoded_image = content::DecodeImage(&encoded_data[0], gfx::Size(),
+                                         encoded_data.size());
+  }
+
+  if (!decoded_image.isNull()) {
+    skia::BitmapPtr dummy_image = skia::Bitmap::New();
+    int64_t struct_size = GetSerializedSize_(dummy_image);
+    int64_t image_size = decoded_image.computeSize64();
+    int halves = 0;
+    while (struct_size + (image_size >> 2 * halves) > max_message_size_)
+      halves++;
+    if (halves) {
+      if (shrink_to_fit) {
+        // If decoded image is too large for IPC message, shrink it by halves.
+        // This prevents quality loss, and should never overshrink on displays
+        // smaller than 3600x2400.
+        // TODO (Issue 416916): Instead of shrinking, return via shared memory
+        decoded_image = skia::ImageOperations::Resize(
+            decoded_image, skia::ImageOperations::RESIZE_LANCZOS3,
+            decoded_image.width() >> halves, decoded_image.height() >> halves);
+      } else {
+        decoded_image.reset();
+      }
+    }
+  }
+
+  if (decoded_image.isNull())
+    callback.Run(nullptr);
+  else
+    callback.Run(skia::Bitmap::From(decoded_image));
+}
+
+}  // namespace image_decoder