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

chrome/browser/web_applications/web_app_win.cc

Index: chrome/browser/web_applications/web_app_win.cc
diff --git a/chrome/browser/web_applications/web_app_win.cc b/chrome/browser/web_applications/web_app_win.cc
index 18772be01290fe04feb78b6704ea1e592d594e23..86e5a0eaa0bd8af8d5afce89dbc1a92abec1d0da 100644
--- a/chrome/browser/web_applications/web_app_win.cc
+++ b/chrome/browser/web_applications/web_app_win.cc
@@ -590,7 +590,7 @@ std::vector<base::FilePath> GetShortcutPaths(
 
   BrowserDistribution* dist = BrowserDistribution::GetDistribution();
   // Populate shortcut_paths.
-  for (int i = 0; i < arraysize(locations); ++i) {
+  for (size_t i = 0; i < arraysize(locations); ++i) {
     if (locations[i].use_this_location) {
       base::FilePath path;
       if (!ShellUtil::GetShortcutPath(locations[i].location_id,