Remove IOThread::message_loop().

Instead introduce BrowserThread::UnsafeGetMessageLoop which is used in
a couple of places.  This will be removed in a follow-up change.  I
could have used UnsafeGetBrowserThread(id)->message_loop() but this is
even easier to search for.

Also, remove a couple of BrowserProcess accessors that aren't used by anybody, and that were using UnsafeGetBrowserThread.

[email protected]
BUG=98716


Review URL: http://codereview.chromium.org/8775014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112697 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index 85d07f2..37bdd925 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -332,7 +332,8 @@
     // of it on shutdown for valid reasons.
     base::ThreadRestrictions::SetIOAllowed(true);
     CHECK(!BrowserList::GetLastActive());
-    io_thread()->message_loop()->PostTask(
+    BrowserThread::PostTask(
+        BrowserThread::IO,
         FROM_HERE,
         base::IgnoreReturn<bool>(
             base::Bind(&base::ThreadRestrictions::SetIOAllowed, true)));
@@ -424,16 +425,6 @@
   return BrowserThread::UnsafeGetBrowserThread(BrowserThread::DB);
 }
 
-base::Thread* BrowserProcessImpl::process_launcher_thread() {
-  DCHECK(CalledOnValidThread());
-  return BrowserThread::UnsafeGetBrowserThread(BrowserThread::PROCESS_LAUNCHER);
-}
-
-base::Thread* BrowserProcessImpl::cache_thread() {
-  DCHECK(CalledOnValidThread());
-  return BrowserThread::UnsafeGetBrowserThread(BrowserThread::CACHE);
-}
-
 WatchDogThread* BrowserProcessImpl::watchdog_thread() {
   DCHECK(CalledOnValidThread());
   if (!created_watchdog_thread_)