Add ios_image_decoder_impl.*

ios/chrome/browser/suggestions/ios_image_decoder_impl.mm

+// 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.
+
+#include "ios/chrome/browser/suggestions/ios_image_decoder_impl.h"
+
+#include <UIKit/UIKit.h>
+
+#include "base/callback.h"
+#include "ui/gfx/image/image.h"
+
+namespace suggestions {
+
+IOSImageDecoderImpl::IOSImageDecoderImpl() {}
+
+IOSImageDecoderImpl::~IOSImageDecoderImpl() {}
+
+void IOSImageDecoderImpl::DecodeImage(
+    const std::string& image_data,
+    const image_fetcher::ImageDecodedCallback& callback) {
+  // Convert the |image_data| std::string to a NSData buffer.
+  NSData* nsData =

[noyau (Ping after 24h), 2016/06/30 08:28:53]

We tend to drop the prefix for variables. s/nsData/data

[markusheintz_, 2016/06/30 09:15:14]

Done.

+      [NSData dataWithBytes:image_data.c_str() length:image_data.length()];

[noyau (Ping after 24h), 2016/06/30 08:28:53]

This causes a copy of the string buffer.

If you use -dataWithBytesNoCopy:length:freeWhenDone:NO you'll get the exact same
behavior, but without the copy. As the string is guaranteed not to be freed
until the method returns, this is safe.

[markusheintz_, 2016/06/30 09:15:14]

c_str or data are returning a const char* . But dataWithBytesNoCopy expects a
non const pointer.

Assume I'm a noob when it comes to objective C and in particular to the
libraries they offer. Maybe I'm missing something obvious.

I could do a cast here.

+
+  // Decode the Image using UIImage.
+  if (nsData) {
+    // Most likely always returns 1x images.
+    UIImage* ui_image = [UIImage imageWithData:nsData scale:1];
+    if (ui_image) {
+      gfx::Image gfx_image(ui_image);
+      callback.Run(gfx_image);
+      return;
+    }
+  }
+  gfx::Image empty_image;
+  callback.Run(empty_image);
+}
+
+}  // namespace suggestions