IWYU fixes in /chrome/browser/themes.

base/win/registry.h includes more than it uses. These files were
inadvertently relying on that fact. This CL adds missing includes so
that registry.h can be cleaned up.

BUG=None
This CL was uploaded by git cl split.

R=pkotwicz@chromium.org

Change-Id: I4d705b912fa264ffaf2c65bac06c47789bb79f5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2475073
Commit-Queue: Peter Kotwicz <pkotwicz@chromium.org>
Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Auto-Submit: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817495}

chrome/browser/themes/theme_helper_win.cc

@@ -5,6 +5,7 @@
 #include "chrome/browser/themes/theme_helper_win.h"
 
 #include "base/bind.h"
+#include "base/callback.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/win/titlebar_config.h"
@@ -291,6 +292,7 @@ void ThemeHelperWin::OnDwmKeyUpdated() {
 
   // Watch for future changes.
   if (!dwm_key_->StartWatching(base::BindOnce(&ThemeHelperWin::OnDwmKeyUpdated,
-                                              base::Unretained(this))))
+                                              base::Unretained(this)))) {
     dwm_key_.reset();
+  }
 }