clang/win: Fix style errors after https://codereview.chromium.org/1585193002

ui/events/keycodes/platform_key_map_win.cc

Index: ui/events/keycodes/platform_key_map_win.cc
diff --git a/ui/events/keycodes/platform_key_map_win.cc b/ui/events/keycodes/platform_key_map_win.cc
index 7fe5cad8cd2218e65c05c53a82b8c13e25d71478..52a44d55838d9c301c8d8caa13ad91f7e55fed1c 100644
--- a/ui/events/keycodes/platform_key_map_win.cc
+++ b/ui/events/keycodes/platform_key_map_win.cc
@@ -44,7 +44,7 @@ const int kModifierFlagsCombinations = (1 << arraysize(modifier_flags)) - 1;
 
 int GetModifierFlags(int combination) {
   int flags = EF_NONE;
-  for (int i = 0; i < arraysize(modifier_flags); ++i) {
+  for (size_t i = 0; i < arraysize(modifier_flags); ++i) {
     if (combination & (1 << i))
       flags |= modifier_flags[i];
   }
@@ -113,6 +113,8 @@ PlatformKeyMap::PlatformKeyMap(HKL layout) {
   UpdateLayout(layout);
 }
 
+PlatformKeyMap::~PlatformKeyMap() {}
+
 DomKey PlatformKeyMap::DomCodeAndFlagsToDomKey(DomCode code, int flags) const {
   const int flags_to_try[] = {
       // Trying to match Firefox's behavior and UIEvents DomKey guidelines.