Uses the correct scale factor for fallback images on iOS.

ui/base/resource/resource_bundle_ios.mm

 // Copyright 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.
 
 #include "ui/base/resource/resource_bundle.h"
 
 #import <QuartzCore/QuartzCore.h>
 #import <UIKit/UIKit.h>
 
 #include "base/basictypes.h"
@@ skipping 115 matching lines @@
       return GetEmptyImage();
     }
 
     // Create a data object from the raw bytes.
     base::scoped_nsobject<NSData> ns_data(
         [[NSData alloc] initWithBytes:data->front() length:data->size()]);
 
     bool is_fallback = PNGContainsFallbackMarker(data->front(), data->size());
     // Create the image from the data.
     CGFloat target_scale = ui::GetScaleForScaleFactor(scale_factor);
-    CGFloat source_scale = is_fallback ? 1.0 : target_scale;
     // Hack: The 200P pak file is the only pak file loaded on iOS devices with
     // an @3x scale factor.  Force |source_scale| to be 2.0 to handle this case,
-    // since it cannot be anything else.
+    // since it cannot be anything else.  http://crbug.com/413300.
     // TODO(rohitrao): Support proper fallback by using the actual scale factor
     // of the source image, rather than assuming it is 1.0 or 2.0.
-    if (scale_factor == SCALE_FACTOR_300P) {
+    CGFloat source_scale = target_scale;
+    if (is_fallback) {
+      source_scale = 1.0;
+    } else if (scale_factor == SCALE_FACTOR_300P) {
       source_scale = 2.0;
     }
     base::scoped_nsobject<UIImage> ui_image(
         [[UIImage alloc] initWithData:ns_data scale:source_scale]);
 
     // If the image is a 1x fallback, scale it up to a full-size representation.
     if (is_fallback) {
       CGSize source_size = [ui_image size];
       CGSize target_size = CGSizeMake(source_size.width * target_scale,
                                       source_size.height * target_scale);
@@ skipping 34 matching lines @@
 
   // Another thread raced the load and has already cached the image.
   if (images_.count(resource_id))
     return images_[resource_id];
 
   images_[resource_id] = image;
   return images_[resource_id];
 }
 
 }  // namespace ui