linux and chromeos: Turn on -Wunused-const-variable.

chrome/browser/ui/views/constrained_window_views.cc

Index: chrome/browser/ui/views/constrained_window_views.cc
diff --git a/chrome/browser/ui/views/constrained_window_views.cc b/chrome/browser/ui/views/constrained_window_views.cc
index f89940ebe3ccdc06b309cc0c563c025a84104566..1309cc221bab39f2eb1d260b43886e936176bb5d 100644
--- a/chrome/browser/ui/views/constrained_window_views.cc
+++ b/chrome/browser/ui/views/constrained_window_views.cc
@@ -323,9 +323,6 @@ namespace {
 // The frame border is only visible in restored mode and is hardcoded to 4 px on
 // each side regardless of the system window border size.
 const int kFrameBorderThickness = 4;
-// Various edges of the frame border have a 1 px shadow along their edges; in a
-// few cases we shift elements based on this amount for visual appeal.
-const int kFrameShadowThickness = 1;
 // In the window corners, the resize areas don't actually expand bigger, but the
 // 16 px at the end of each edge triggers diagonal resizing.
 const int kResizeAreaCornerSize = 16;