Fixed all unused-variable Clang warnings on Windows.

ui/gfx/win/dpi.cc

Index: ui/gfx/win/dpi.cc
diff --git a/ui/gfx/win/dpi.cc b/ui/gfx/win/dpi.cc
index ceaaefde8876a7082316105178ecf58ef02733ff..aa3194c388eab5e0f3240eefb701175a777a4e62 100644
--- a/ui/gfx/win/dpi.cc
+++ b/ui/gfx/win/dpi.cc
@@ -13,10 +13,7 @@
 
 namespace {
 
-int kDefaultDPIX = 96;
-int kDefaultDPIY = 96;
-
-bool force_highdpi_for_testing = false;
+int kDefaultDPI = 96;
 
 float g_device_scale_factor = 0.0f;
 
@@ -26,7 +23,7 @@ float GetUnforcedDeviceScaleFactor() {
   if (g_device_scale_factor)
     return g_device_scale_factor;
   return static_cast<float>(gfx::GetDPI().width()) /
-      static_cast<float>(kDefaultDPIX);
+      static_cast<float>(kDefaultDPI);
 }
 
 }  // namespace