clang/win: Let some chromium_code targets build with -Wextra.

content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc

Index: content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc
diff --git a/content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc b/content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc
index 13382a8656fb72791ec3bf19bfb286492285d691..15c9f88cbe7cf1c2814791dfd13816218bf99703 100644
--- a/content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc
+++ b/content/browser/web_contents/aura/overscroll_window_delegate_unittest.cc
@@ -54,11 +54,9 @@ class OverscrollWindowDelegateTest : public aura::test::AuraTestBase,
 
   OverscrollMode current_mode() { return current_mode_; }
 
-  const float touch_start_threshold() {
-    return touch_start_threshold_;
-  }
+  float touch_start_threshold() { return touch_start_threshold_; }
 
-  const float touch_complete_threshold() {
+  float touch_complete_threshold() {
     return kTestWindowWidth * touch_complete_threshold_;
   }