Support copying a partial rectangle region from the compositing surface on Win.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 8ed673b2a33ecfb2a9199410954a712db5f39b38..2e52c27c07d789dbe38fae7f855ce3f00848c84a 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -503,14 +503,8 @@ void RenderWidgetHostImpl::CopyFromBackingStore(
   if (view_ && is_accelerated_compositing_active_) {
     TRACE_EVENT0("browser",
         "RenderWidgetHostImpl::CopyFromBackingStore::FromCompositingSurface");
-#if defined(USE_AURA) || defined(OS_LINUX) || defined(OS_MACOSX)
     gfx::Rect copy_rect = src_subrect.IsEmpty() ?
         gfx::Rect(view_->GetViewBounds().size()) : src_subrect;
-#else
-    // Just passes an empty rect to CopyFromCompositingSurface on non-Aura Win
-    // because copying a partial rectangle is not supported.
-    gfx::Rect copy_rect;
-#endif
     view_->CopyFromCompositingSurface(copy_rect,
                                       accelerated_dst_size,
                                       callback,