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

Chrome iOS is moving to Objective-C Automatic Reference Counting. Under
it, arguments are supposed to be autoreleased. This CL adds a new
constructor that can take both a retained and an autoreleased object.
This is a part of a multiple CL setup that will change the Image(UIImage*) constructor from consuming +1 refcount to retaining the argument.

TEST=none
BUG=645125

Review-Url: https://codereview.chromium.org/2504683002
Cr-Commit-Position: refs/heads/master@{#437513}

ios/chrome/browser/suggestions/image_fetcher_impl.mm

@@ -61,7 +61,7 @@ void ImageFetcherImpl::StartOrQueueNetworkRequest(
           // Most likely always returns 1x images.
           UIImage* ui_image = [UIImage imageWithData:data scale:1];
           if (ui_image) {
-            gfx::Image gfx_image(ui_image);
+            gfx::Image gfx_image(ui_image, base::scoped_policy::ASSUME);
             callback.Run(fetch_id, gfx_image);
             if (delegate_) {
               delegate_->OnImageFetched(fetch_id, gfx_image);

ios/chrome/browser/suggestions/ios_image_decoder_impl.mm

@@ -148,7 +148,7 @@ void IOSImageDecoderImpl::CreateUIImageAndRunCallback(
       // This constructor does not retain the image, but expects to take the
       // ownership, therefore, |ui_image| is retained here, but not released
       // afterwards.
-      gfx::Image gfx_image([ui_image retain]);
+      gfx::Image gfx_image(ui_image, base::scoped_policy::RETAIN);
       callback.Run(gfx_image);
       return;
     }

ui/base/resource/resource_bundle_ios.mm

@@ -163,7 +163,7 @@ gfx::Image& ResourceBundle::GetNativeImageNamed(int resource_id) {
     }
 
     // The gfx::Image takes ownership.
-    image = gfx::Image(ui_image.release());
+    image = gfx::Image(ui_image, base::scoped_policy::RETAIN);
   }
 
   base::AutoLock lock(*images_and_fonts_lock_);

ui/gfx/image/image.cc

@@ -420,10 +420,15 @@ Image::Image(const ImageSkia& image) {
 }
 
 #if defined(OS_IOS)
-Image::Image(UIImage* image)
+Image::Image(UIImage* image) : Image(image, base::scoped_policy::ASSUME) {}
+
+Image::Image(UIImage* image, base::scoped_policy::OwnershipPolicy policy)
     : storage_(new internal::ImageStorage(Image::kImageRepCocoaTouch)) {
-  if (image)
+  if (image) {
+    if (policy == base::scoped_policy::RETAIN)
+      base::mac::NSObjectRetain(image);
     AddRepresentation(base::MakeUnique<internal::ImageRepCocoaTouch>(image));
+  }
 }
 #elif defined(OS_MACOSX)
 Image::Image(NSImage* image) {

ui/gfx/image/image.h

@@ -26,6 +26,7 @@
 #include <vector>
 
 #include "base/memory/ref_counted_memory.h"
+#include "base/memory/scoped_policy.h"
 #include "build/build_config.h"
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/native_widget_types.h"
@@ -72,6 +73,10 @@ class GFX_EXPORT Image {
 #if defined(OS_IOS)
   // Does not retain |image|; expects to take ownership.
   explicit Image(UIImage* image);
+
+  // Retains argument according to |policy|.
+  Image(UIImage* image, base::scoped_policy::OwnershipPolicy policy);
+
 #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