Replace instances of LINUX2 with OS_CHROMEOS and linux2 with chromeos.

chrome/browser/browser_init.cc

Index: chrome/browser/browser_init.cc
diff --git a/chrome/browser/browser_init.cc b/chrome/browser/browser_init.cc
index e9690b593f668eecfdf9dcb2848e7c3ed0e8a7c6..fdb85eaac972d4d384ee302da99c2984ce68dacc 100644
--- a/chrome/browser/browser_init.cc
+++ b/chrome/browser/browser_init.cc
@@ -60,7 +60,7 @@
 #include "base/win_util.h"
 #endif
 
-#if defined(LINUX2)
+#if defined(OS_CHROMEOS)
 #include "chrome/browser/views/tabs/tab_overview_message_listener.h"
 #endif
 
@@ -341,7 +341,7 @@ bool LaunchBrowser(const CommandLine& command_line, Profile* profile,
     return false;
   }
 
-#if defined(LINUX2)
+#if defined(OS_CHROMEOS)
   // Create the TabOverviewMessageListener so that it can listen for messages
   // regardless of what window has focus.
   TabOverviewMessageListener::instance();