gdata: Convert FindEntryByResourceIdSync() to asynchronous.

chrome/browser/chromeos/gdata/gdata_file_system.cc

Index: chrome/browser/chromeos/gdata/gdata_file_system.cc
diff --git a/chrome/browser/chromeos/gdata/gdata_file_system.cc b/chrome/browser/chromeos/gdata/gdata_file_system.cc
index c73dd2ef28ce7efee16403340e8856313aba483c..871b3ebecacb646ffb14486b25c6d4453364f9ee 100644
--- a/chrome/browser/chromeos/gdata/gdata_file_system.cc
+++ b/chrome/browser/chromeos/gdata/gdata_file_system.cc
@@ -1041,11 +1041,24 @@ void GDataFileSystem::Authenticate(const AuthStatusCallback& callback) {
   documents_service_->Authenticate(callback);
 }
 
-void GDataFileSystem::FindEntryByResourceIdSync(
+void GDataFileSystem::FindEntryByResourceIdAsync(
     const std::string& resource_id,
     const FindEntryCallback& callback) {
-  base::AutoLock lock(lock_);  // To access root.
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||

[achuithb, 2012/06/11 20:46:37]

Not sure I understand the point of this DCHECK?

[hshi1, 2012/06/11 20:58:51]

This is essentially a copy & paste of the many other functions (such as
GetEntryInfoByPathAsync and ReadDirectoryByPathAsync). In principle it is not
necessary as the RunTaskOnUIThread ensures the task will be run on UI, but it
seems that we expect the entry to be called on UI or IO thread.

[achuithb, 2012/06/11 21:48:41]

I've not seen this pattern before (outside of this file). And in this particular
case it really does seem pointless since the only thing you do is schedule on
the UI thread. But you can leave it in for consistency.

+         BrowserThread::CurrentlyOn(BrowserThread::IO));
+  RunTaskOnUIThread(
+      base::Bind(&GDataFileSystem::FindEntryByResourceIdAsyncOnUIThread,
+                 ui_weak_ptr_,
+                 resource_id,
+                 CreateRelayCallback(callback)));
+}
+
+void GDataFileSystem::FindEntryByResourceIdAsyncOnUIThread(
+    const std::string& resource_id,
+    const FindEntryCallback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
+  base::AutoLock lock(lock_);  // To access root.
   GDataFile* file = NULL;
   GDataEntry* entry = root_->GetEntryByResourceId(resource_id);
   if (entry)