Fix CopyFromBackingStore when there's no cg_layer_.

content/browser/renderer_host/backing_store_mac.mm

 // 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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "content/browser/renderer_host/backing_store_mac.h"
 
 #include <cmath>
 
@@ skipping 144 matching lines @@
       CGContextDrawImage(layer, paint_rect.ToCGRect(), image);
     } else {
       // The layer hasn't been created yet, so draw into the cache bitmap.
       gfx::Rect paint_rect = copy_rect;
       paint_rect.set_y(size().height() - copy_rect.bottom());
       CGContextDrawImage(cg_bitmap_, paint_rect.ToCGRect(), image);
     }
   }
 }
 
 bool BackingStoreMac::CopyFromBackingStore(const gfx::Rect& rect,

[Nico, 2013/07/01 16:55:00]

for hidpi: one probably would hand in a scale factor output is desired in too
(or hand it out if this always uses the backing store's scale factor), then
allocate the output at pixel size rect * scale, and apply a scale to
temp_context if necessary.

                                            skia::PlatformBitmap* output) {
   // TODO(thakis): Make sure this works with HiDPI backing stores.
   if (!output->Allocate(rect.width(), rect.height(), true))
     return false;
 
   CGContextRef temp_context = output->GetSurface();
   gfx::ScopedCGContextSaveGState save_gstate(temp_context);
   CGContextTranslateCTM(temp_context, 0.0, size().height());

[Nico, 2013/07/01 16:55:00]

size() returns logical size, which isn't right for mirroring in y. This should
probably use rect.height() instead, possibly scaled by the output scale factor
if necessary (if the output scale factor is different from the backing store's).

   CGContextScaleCTM(temp_context, 1.0, -1.0);
-  CGContextDrawLayerAtPoint(temp_context, CGPointMake(-rect.x(), -rect.y()),
-                            cg_layer());
+  if (cg_layer()) {
+    CGContextDrawLayerAtPoint(temp_context, CGPointMake(-rect.x(), -rect.y()),
+                              cg_layer());
+  } else {
+    base::ScopedCFTypeRef<CGImageRef> bitmap_image(
+        CGBitmapContextCreateImage(cg_bitmap_));
+    CGContextDrawImage(
+        temp_context,
+        CGRectMake(-rect.x(), -rect.y(), rect.width(), rect.height()),
+        bitmap_image);
+  }
+
   return true;
 }
 
 // Scroll the contents of our CGLayer
 void BackingStoreMac::ScrollBackingStore(const gfx::Vector2d& delta,
                                          const gfx::Rect& clip_rect,
                                          const gfx::Size& view_size) {
   DCHECK_NE(static_cast<bool>(cg_layer()), static_cast<bool>(cg_bitmap()));
 
   // "Scroll" the contents of the layer by creating a new CGLayer,
@@ skipping 91 matching lines @@
                                                8, pixel_size.width() * 4,
                                                base::mac::GetSystemColorSpace(),
                                                kCGImageAlphaPremultipliedFirst |
                                                    kCGBitmapByteOrder32Host);
   DCHECK(context);
 
   return context;
 }
 
 }  // namespace content