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

content/browser/renderer_host/render_widget_host_view_win.cc

 // 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_win.h"
 
 #include <algorithm>
 #include <map>
 #include <peninputpanel_i.c>
 #include <stack>
@@ skipping 1379 matching lines @@
       // Grabbing the damaged regions failed, fake with the whole rect.
       data_size = sizeof(RGNDATAHEADER) + sizeof(RECT);
       region_data_buf.reset(new char[data_size]);
       region_data = reinterpret_cast<RGNDATA*>(region_data_buf.get());
       region_rects = reinterpret_cast<RECT*>(region_data->Buffer);
       region_data->rdh.nCount = 1;
       region_rects[0] = damaged_rect.ToRECT();
     }
 
     for (DWORD i = 0; i < region_data->rdh.nCount; ++i) {
-      gfx::Rect paint_rect = bitmap_rect.Intersect(gfx::Rect(region_rects[i]));
+      gfx::Rect paint_rect = bitmap_rect;
+      paint_rect.Intersect(gfx::Rect(region_rects[i]));
       if (!paint_rect.IsEmpty()) {
         BitBlt(paint_dc.m_hDC,
                paint_rect.x(),
                paint_rect.y(),
                paint_rect.width(),
                paint_rect.height(),
                backing_store->hdc(),
                paint_rect.x(),
                paint_rect.y(),
                SRCCOPY);
@@ skipping 1719 matching lines @@
   // receive a focus change in the context of a pointer down message, it means
   // that the pointer down message occurred on the edit field and we should
   // display the on screen keyboard
   if (!received_focus_change_after_pointer_down_ && virtual_keyboard_)
     DisplayOnScreenKeyboardIfNeeded();
   received_focus_change_after_pointer_down_ = false;
   pointer_down_context_ = false;
 }
 
 }  // namespace content