Add non-member non-mutating methods for common gfx::Rect operations.

ui/gfx/blit.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 "ui/gfx/blit.h"
 
 #include "base/logging.h"
 #include "build/build_config.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/gfx/point.h"
@@ skipping 134 matching lines @@
 #endif  // defined(OS_WIN)
   // For non-windows, always do scrolling in software.
   // Cairo has no nice scroll function so we do our own. On Mac it's possible to
   // use platform scroll code, but it's complex so we just use the same path
   // here. Either way it will be software-only, so it shouldn't matter much.
   SkBitmap& bitmap = const_cast<SkBitmap&>(
       skia::GetTopDevice(*canvas)->accessBitmap(true));
   SkAutoLockPixels lock(bitmap);
 
   // We expect all coords to be inside the canvas, so clip here.
-  gfx::Rect clip = in_clip;
-  clip.Intersect(gfx::Rect(0, 0, bitmap.width(), bitmap.height()));
+  gfx::Rect clip = gfx::IntersectRects(
+      in_clip, gfx::Rect(0, 0, bitmap.width(), bitmap.height()));
 
   // Compute the set of pixels we'll actually end up painting.
   gfx::Rect dest_rect = clip;
   dest_rect.Offset(amount);
   dest_rect.Intersect(clip);
   if (dest_rect.size() == gfx::Size())
     return;  // Nothing to do.
 
   // Compute the source pixels that will map to the dest_rect
   gfx::Rect src_rect = dest_rect;
@@ skipping 20 matching lines @@
     // Fortunately, memmove already handles this for us.
     for (int y = 0; y < dest_rect.height(); y++) {
       memmove(bitmap.getAddr32(dest_rect.x(), dest_rect.y() + y),
               bitmap.getAddr32(src_rect.x(), src_rect.y() + y),
               row_bytes);
     }
   }
 }
 
 }  // namespace gfx