Migrate BrowserThread::IsMessageLoopValid to BrowserThread::IsThreadInitialized.

The two methods converged over the last year and are now equivalent.

Bug: 825054
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I4ec5f7afb5b7b21278af6c777efe9ad57d2aae68
Reviewed-on: https://chromium-review.googlesource.com/977063
Reviewed-by: John Abd-El-Malek <[email protected]>
Commit-Queue: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#546529}
diff --git a/content/browser/browser_context.cc b/content/browser/browser_context.cc
index 91f87bb..15cb62d7 100644
--- a/content/browser/browser_context.cc
+++ b/content/browser/browser_context.cc
@@ -233,7 +233,7 @@
   // Ensure that these methods are called on the UI thread, except for
   // unittests where a UI thread might not have been created.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
-         !BrowserThread::IsMessageLoopValid(BrowserThread::UI));
+         !BrowserThread::IsThreadInitialized(BrowserThread::UI));
 
 #if defined(OS_CHROMEOS)
   if (!context->GetUserData(kMountPointsKey)) {
@@ -433,7 +433,7 @@
       base::BindOnce(&storage::DatabaseTracker::SetForceKeepSessionState,
                      base::WrapRefCounted(database_tracker)));
 
-  if (BrowserThread::IsMessageLoopValid(BrowserThread::IO)) {
+  if (BrowserThread::IsThreadInitialized(BrowserThread::IO)) {
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE,
         base::BindOnce(