Adds a new constructor for gfx::Image on iOS.

ui/gfx/image/image.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.
 
 // An Image wraps an image any flavor, be it platform-native GdkBitmap/NSImage,
 // or a SkBitmap. This also provides easy conversion to other image types
 // through operator overloading. It will cache the converted representations
 // internally to prevent double-conversion.
 //
 // The lifetime of both the initial representation and any converted ones are
@@ skipping 54 matching lines @@
   // default representation.
   explicit Image(const std::vector<ImagePNGRep>& image_reps);
 
   // Creates a new image by copying the ImageSkia for use as the default
   // representation.
   explicit Image(const ImageSkia& image);
 
 #if defined(OS_IOS)
   // Does not retain |image|; expects to take ownership.
   explicit Image(UIImage* image);
+
+  // Retains argument if |retain_argument| is true.
+  explicit Image(UIImage* image, bool retain_argument);

[sdefresne, 2016/11/22 14:23:16]

"explicit" is only for constructor that can be invoked with exactly one
argument. This is not the case here, so remove "explicit".

I don't really like using a bool parameter as it is always hard to understand
the call-sites. Since base::scoped_policy::OwnershipPolicy exists, can you use
that instead of a bool?

[stkhapugin, 2016/12/06 10:41:57]

Done

+
 #elif defined(OS_MACOSX)
   // Does not retain |image|; expects to take ownership.
   // A single NSImage object can contain multiple bitmaps so there's no reason
   // to pass a vector of these.
   explicit Image(NSImage* image);
 #endif
 
   // Initializes a new Image by AddRef()ing |other|'s internal storage.
   Image(const Image& other);
 
@@ skipping 105 matching lines @@
       std::unique_ptr<internal::ImageRep> rep) const;
 
   // Internal class that holds all the representations. This allows the Image to
   // be cheaply copied.
   scoped_refptr<internal::ImageStorage> storage_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_IMAGE_IMAGE_H_