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

webkit/tools/test_shell/webwidget_host_win.cc

 // Copyright (c) 2011 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 "webkit/tools/test_shell/webwidget_host.h"
 
 #include "base/logging.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPopupMenu.h"
@@ skipping 231 matching lines @@
     canvas_.reset(new skia::PlatformCanvas(
         paint_rect_.width(), paint_rect_.height(), true));
   }
 
   webwidget_->animate(0.0);
 
   // This may result in more invalidation
   webwidget_->layout();
 
   // Scroll the canvas if necessary
-  scroll_rect_ = client_rect.Intersect(scroll_rect_);
+  scroll_rect_.Intersect(client_rect);
   if (!scroll_rect_.IsEmpty()) {
     skia::ScopedPlatformPaint scoped_platform_paint(canvas_.get());
     HDC hdc = scoped_platform_paint.GetPlatformSurface();
 
     RECT damaged_rect, r = scroll_rect_.ToRECT();
     ScrollDC(hdc, scroll_dx_, scroll_dy_, NULL, &r, NULL, &damaged_rect);
 
     PaintRect(gfx::Rect(damaged_rect));
   }
   ResetScrollRect();
 
   // Paint the canvas if necessary.  Allow painting to generate extra rects the
   // first time we call it.  This is necessary because some WebCore rendering
   // objects update their layout only when painted.
   for (int i = 0; i < 2; ++i) {
-    paint_rect_ = client_rect.Intersect(paint_rect_);
+    paint_rect_.Intersect(client_rect);
     if (!paint_rect_.IsEmpty()) {
       gfx::Rect rect(paint_rect_);
       paint_rect_ = gfx::Rect();
 
       DLOG_IF(WARNING, i == 1) << "painting caused additional invalidations";
       PaintRect(rect);
     }
   }
   DCHECK(paint_rect_.IsEmpty());
 
@@ skipping 94 matching lines @@
 void WebWidgetHost::PaintRect(const gfx::Rect& rect) {
 #ifndef NDEBUG
   DCHECK(!painting_);
 #endif
   DCHECK(canvas_.get());
 
   set_painting(true);
   webwidget_->paint(canvas_.get(), rect);
   set_painting(false);
 }