Display skips swapping if overlays draw the damage

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 1677de1ccc083300f6b81dc0bac0e10da0dd545b..f6e1114aea362340d77d8cb3617743958a848a92 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -2607,23 +2607,18 @@ void GLRenderer::SwapBuffers(const CompositorFrameMetadata& metadata) {
   compositor_frame.metadata = metadata;
   compositor_frame.gl_frame_data = make_scoped_ptr(new GLFrameData);
   compositor_frame.gl_frame_data->size = surface_size;
-  if (capabilities_.using_partial_swap) {
-    // If supported, we can save significant bandwidth by only swapping the
-    // damaged/scissored region (clamped to the viewport).
-    swap_buffer_rect_.Intersect(gfx::Rect(surface_size));
-    int flipped_y_pos_of_rect_bottom = surface_size.height() -
-                                       swap_buffer_rect_.y() -
-                                       swap_buffer_rect_.height();
-    compositor_frame.gl_frame_data->sub_buffer_rect =
-        gfx::Rect(swap_buffer_rect_.x(),
-                  FlippedRootFramebuffer() ? flipped_y_pos_of_rect_bottom
-                                           : swap_buffer_rect_.y(),
-                  swap_buffer_rect_.width(),
-                  swap_buffer_rect_.height());
-  } else {
-    compositor_frame.gl_frame_data->sub_buffer_rect =
-        gfx::Rect(output_surface_->SurfaceSize());
-  }
+  // If supported, we can save significant bandwidth by only swapping the
+  // damaged/scissored region (clamped to the viewport). The surface can
+  // choose whether to do a full swap or partial swap.

[piman, 2015/11/19 21:22:04]

If we do that we need to fix all the OutputSurface implementations. See e.g.
GpuBrowserCompositorOutputSurface::SwapBuffers

+  swap_buffer_rect_.Intersect(gfx::Rect(surface_size));
+  int flipped_y_pos_of_rect_bottom = surface_size.height() -
+                                     swap_buffer_rect_.y() -
+                                     swap_buffer_rect_.height();
+  compositor_frame.gl_frame_data->sub_buffer_rect =
+      gfx::Rect(swap_buffer_rect_.x(),
+                FlippedRootFramebuffer() ? flipped_y_pos_of_rect_bottom
+                                         : swap_buffer_rect_.y(),
+                swap_buffer_rect_.width(), swap_buffer_rect_.height());
   output_surface_->SwapBuffers(&compositor_frame);
 
   // We always hold onto resources for an extra frame, to make sure we don't