HUD: Show first paint invalidation in red

cc/debug/debug_rect_history.cc

Index: cc/debug/debug_rect_history.cc
diff --git a/cc/debug/debug_rect_history.cc b/cc/debug/debug_rect_history.cc
index e8792e7789e884451ffc7800d38741813fbf7021..d6ef8c1767c69406cc6a1d09b853a4847fa98bdf 100644
--- a/cc/debug/debug_rect_history.cc
+++ b/cc/debug/debug_rect_history.cc
@@ -77,6 +77,8 @@ void DebugRectHistory::SavePaintRects(LayerImpl* layer) {
   // surface list.
 
   if (!layer->update_rect().IsEmpty() && layer->DrawsContent()) {
+    bool is_first_paint = layer->includes_first_paint_invalidation();
+
     float width_scale = layer->content_bounds().width() /
                         static_cast<float>(layer->bounds().width());
     float height_scale = layer->content_bounds().height() /
@@ -84,7 +86,7 @@ void DebugRectHistory::SavePaintRects(LayerImpl* layer) {
     gfx::Rect update_content_rect = gfx::ScaleToEnclosingRect(
         gfx::ToEnclosingRect(layer->update_rect()), width_scale, height_scale);
     debug_rects_.push_back(
-        DebugRect(PAINT_RECT_TYPE,
+        DebugRect(is_first_paint ? FIRST_PAINT_RECT_TYPE : PAINT_RECT_TYPE,
                   MathUtil::MapEnclosingClippedRect(
                       layer->screen_space_transform(), update_content_rect)));
   }