ui: Add debug flag to show composited layer borders in ChromeOS UI.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 26d36e028890b08e3483aec8ca02b2c6a4e3aaee..fbb1745c629bc79062ec1cd3a1a02f68f6a9b818 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -253,7 +253,7 @@ void PictureLayerImpl::AppendQuads(RenderPass* render_pass,
   AppendDebugBorderQuad(render_pass, shared_quad_state->quad_layer_bounds,
                         shared_quad_state, append_quads_data);
 
-  if (ShowDebugBorders()) {
+  if (ShowDebugBorders(DebugBorderType::LAYER)) {
     for (PictureLayerTilingSet::CoverageIterator iter(
              tilings_.get(), max_contents_scale,
              shared_quad_state->visible_quad_layer_rect, ideal_contents_scale_);
@@ -378,7 +378,7 @@ void PictureLayerImpl::AppendQuads(RenderPass* render_pass,
     if (!has_draw_quad) {
       // Checkerboard.
       SkColor color = SafeOpaqueBackgroundColor();
-      if (ShowDebugBorders()) {
+      if (ShowDebugBorders(DebugBorderType::LAYER)) {
         // Fill the whole tile with the missing tile color.
         color = DebugColors::OOMTileBorderColor();
       }