cc: Fix invalid opaque debug quads

It's possible that small debug border quads (when opaque) can get inset
so much that they become empty.  This causes problems in IPC validating,
as the quad rect no longer contains the visible rect (which is empty,
due to the insetting).  This causes the frame to be invalid, which
causes browser rendering artifacts.

BUG=472014

Review URL: https://codereview.chromium.org/1105573002

Cr-Commit-Position: refs/heads/master@{#326618}

cc/layers/layer_impl.cc

@@ -352,6 +352,8 @@ void LayerImpl::AppendDebugBorderQuad(RenderPass* render_pass,
     float fill_width = width * 3;
     gfx::Rect fill_rect = quad_rect;
     fill_rect.Inset(fill_width / 2.f, fill_width / 2.f);
+    if (fill_rect.IsEmpty())
+      return;
     gfx::Rect visible_fill_rect =
         gfx::IntersectRects(visible_quad_rect, fill_rect);
     DebugBorderDrawQuad* fill_quad =