Refactor OS_LINUX preprocessor directive for LaCrOS effort.

Currently, ChromeOS defines the OS_LINUX directive as well as
OS_CHROMEOS.  We're working to separate these two, so we're
making the fact that OS_LINUX == OS_LINUX || OS_CHROMEOS
explicit.

This is changes for /chrome/browser/notifications

This CL was uploaded by git cl split.

R=yoshiki@chromium.org

Bug: 1110266
Change-Id: Ia3805830c319754c760ddf58fddba687f33d68c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2371256Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Sean McAllister <smcallis@google.com>
Cr-Commit-Position: refs/heads/master@{#801273}

chrome/browser/notifications/notification_display_service_impl.cc

@@ -37,7 +37,8 @@
 #include "chrome/browser/notifications/notification_platform_bridge_message_center.h"
 #endif
 
-#if defined(OS_LINUX) || defined(OS_MAC) || defined(OS_WIN)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS) || defined(OS_MAC) || \
+    defined(OS_WIN)
 #include "chrome/browser/nearby_sharing/nearby_notification_handler.h"
 #include "chrome/browser/send_tab_to_self/desktop_notification_handler.h"
 #include "chrome/browser/sharing/sharing_notification_handler.h"
@@ -52,7 +53,7 @@ namespace {
 
 #if !defined(OS_CHROMEOS)
 bool NativeNotificationsEnabled(Profile* profile) {
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
   if (profile) {
     PrefService* prefs = profile->GetPrefs();
     if (!prefs->GetBoolean(prefs::kAllowNativeNotifications))
@@ -151,7 +152,8 @@ NotificationDisplayServiceImpl::NotificationDisplayServiceImpl(Profile* profile)
     AddNotificationHandler(NotificationHandler::Type::WEB_PERSISTENT,
                            std::make_unique<PersistentNotificationHandler>());
 
-#if defined(OS_LINUX) || defined(OS_MAC) || defined(OS_WIN)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS) || defined(OS_MAC) || \
+    defined(OS_WIN)
     AddNotificationHandler(
         NotificationHandler::Type::SEND_TAB_TO_SELF,
         std::make_unique<send_tab_to_self::DesktopNotificationHandler>(

chrome/browser/notifications/notification_interactive_uitest.cc

@@ -442,7 +442,7 @@ IN_PROC_BROWSER_TEST_F(NotificationsTest, TestCloseTabWithPermissionRequestUI) {
 }
 
 // See crbug.com/248470
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
 #define MAYBE_TestCrashRendererNotificationRemain \
     DISABLED_TestCrashRendererNotificationRemain
 #else