Extensions: Prevent URLPatternSet copies.

This CL prevents redundant copies of URLPatternSet at certain locations by
taking a const reference.

BUG=None

Change-Id: Ib44686f30e10bd03a4e05b925cf4f1664b30bd34
Reviewed-on: https://chromium-review.googlesource.com/890044Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532170}

chrome/browser/extensions/crx_installer.cc

@@ -458,7 +458,7 @@ CrxInstallError CrxInstaller::AllowInstall(const Extension* extension) {
       pattern.SetHost(download_url_.host());
       pattern.SetMatchSubdomains(true);
 
-      URLPatternSet patterns = extension_->web_extent();
+      const URLPatternSet& patterns = extension_->web_extent();
       for (URLPatternSet::const_iterator i = patterns.begin();
            i != patterns.end(); ++i) {
         if (!pattern.MatchesHost(i->host())) {

chrome/browser/ui/webui/settings/site_settings_handler.cc

@@ -92,7 +92,7 @@ void AddExceptionsGrantedByHostedApps(content::BrowserContext* context,
         !(*extension)->permissions_data()->HasAPIPermission(permission))
       continue;
 
-    extensions::URLPatternSet web_extent = (*extension)->web_extent();
+    const extensions::URLPatternSet& web_extent = (*extension)->web_extent();
     // Add patterns from web extent.
     for (extensions::URLPatternSet::const_iterator pattern = web_extent.begin();
          pattern != web_extent.end(); ++pattern) {

extensions/browser/api/management/management_api.cc

@@ -186,7 +186,7 @@ management::ExtensionInfo CreateExtensionInfo(
 
   if (!extension.is_hosted_app()) {
     // Skip host permissions for hosted apps.
-    const URLPatternSet host_perms =
+    const URLPatternSet& host_perms =
         extension.permissions_data()->active_permissions().explicit_hosts();
     if (!host_perms.is_empty()) {
       for (URLPatternSet::const_iterator iter = host_perms.begin();