Make gfx::Rect class operations consistently mutate the class they are called on.

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 83 matching lines @@
     bool* scheduled_completion_callback) {
   *scheduled_completion_callback = false;
   DCHECK_NE(static_cast<bool>(cg_layer()), static_cast<bool>(cg_bitmap()));
 
   TransportDIB* dib = process->GetTransportDIB(bitmap);
   if (!dib)
     return;
 
   gfx::Size pixel_size = gfx::ToFlooredSize(
       size().Scale(device_scale_factor_));
-  gfx::Rect pixel_bitmap_rect =
-      ToFlooredRect(bitmap_rect.Scale(scale_factor));
+  gfx::RectF scaled_bitmap_rect = bitmap_rect;
+  scaled_bitmap_rect.Scale(scale_factor);
+  gfx::Rect pixel_bitmap_rect = ToFlooredRect(scaled_bitmap_rect);
 
   size_t bitmap_byte_count =
       pixel_bitmap_rect.width() * pixel_bitmap_rect.height() * 4;
   DCHECK_GE(dib->size(), bitmap_byte_count);
 
   base::mac::ScopedCFTypeRef<CGDataProviderRef> data_provider(
       CGDataProviderCreateWithData(NULL, dib->memory(),
       bitmap_byte_count, NULL));
 
   base::mac::ScopedCFTypeRef<CGImageRef> bitmap_image(
       CGImageCreate(pixel_bitmap_rect.width(), pixel_bitmap_rect.height(),
           8, 32, 4 * pixel_bitmap_rect.width(),
           base::mac::GetSystemColorSpace(),
           kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host,
           data_provider, NULL, false, kCGRenderingIntentDefault));
 
   for (size_t i = 0; i < copy_rects.size(); i++) {
     const gfx::Rect& copy_rect = copy_rects[i];
-    gfx::Rect pixel_copy_rect =
-        ToFlooredRect(copy_rect.Scale(scale_factor));
+    gfx::RectF scaled_copy_rect = copy_rect;
+    scaled_copy_rect.Scale(scale_factor);
+    gfx::Rect pixel_copy_rect = ToFlooredRect(scaled_copy_rect);
 
     // Only the subpixels given by copy_rect have pixels to copy.
     base::mac::ScopedCFTypeRef<CGImageRef> image(
         CGImageCreateWithImageInRect(bitmap_image, CGRectMake(
             pixel_copy_rect.x() - pixel_bitmap_rect.x(),
             pixel_copy_rect.y() - pixel_bitmap_rect.y(),
             pixel_copy_rect.width(),
             pixel_copy_rect.height())));
 
     if (!cg_layer()) {
@@ skipping 142 matching lines @@
                                                8, pixel_size.width() * 4,
                                                base::mac::GetSystemColorSpace(),
                                                kCGImageAlphaPremultipliedFirst |
                                                    kCGBitmapByteOrder32Host);
   DCHECK(context);
 
   return context;
 }
 
 }  // namespace content