Fix PreRunValidation calls in two of UIThreadExtensionFunction's subclasses.

From what I can tell, skipping base (UITEF) class's PreRunValidation isn't
a good idea. Make those subclasses include calling the base function.

The two subclasses are:
AppCurrentWindowInternalExtensionFunction and
FileSystemProviderInternalFunction

BUG=None
Test=None, in theory we should correctly send errors to extension APIs when
browser is shutting down.

Review-Url: https://codereview.chromium.org/2617023003
Cr-Commit-Position: refs/heads/master@{#441839}

chrome/browser/chromeos/extensions/file_system_provider/provider_function.cc

@@ -147,6 +147,9 @@ FileSystemProviderInternalFunction::FulfillRequest(
 }
 
 bool FileSystemProviderInternalFunction::PreRunValidation(std::string* error) {
+  if (!UIThreadExtensionFunction::PreRunValidation(error))
+    return false;
+
   std::string file_system_id;
 
   EXTENSION_FUNCTION_PRERUN_VALIDATE(args_->GetString(0, &file_system_id));

extensions/browser/api/app_current_window_internal/app_current_window_internal_api.cc

@@ -122,6 +122,9 @@ BoundsType GetBoundsType(const std::string& type_as_string) {
 
 bool AppCurrentWindowInternalExtensionFunction::PreRunValidation(
     std::string* error) {
+  if (!UIThreadExtensionFunction::PreRunValidation(error))
+    return false;
+
   AppWindowRegistry* registry = AppWindowRegistry::Get(browser_context());
   DCHECK(registry);
   content::WebContents* web_contents = GetSenderWebContents();