Introduce the plumbing necessary to report Unrecoverable error from model safe workers.

chrome/browser/sync/engine/model_safe_worker.h

Index: chrome/browser/sync/engine/model_safe_worker.h
diff --git a/chrome/browser/sync/engine/model_safe_worker.h b/chrome/browser/sync/engine/model_safe_worker.h
index f4829ec4b58140f9d37d57541ff0bb7ac4d25c38..ee04e00982b1df03d2a708f0f0e7c916b5c33f50 100644
--- a/chrome/browser/sync/engine/model_safe_worker.h
+++ b/chrome/browser/sync/engine/model_safe_worker.h
@@ -13,6 +13,7 @@
 #include "base/callback_old.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/sync/syncable/model_type.h"
+#include "chrome/browser/sync/sessions/unrecoverable_error_info.h"
 
 namespace base {
 class DictionaryValue;
@@ -52,7 +53,9 @@ class ModelSafeWorker : public base::RefCountedThreadSafe<ModelSafeWorker> {
   // Any time the Syncer performs model modifications (e.g employing a
   // WriteTransaction), it should be done by this method to ensure it is done
   // from a model-safe thread.
-  virtual void DoWorkAndWaitUntilDone(Callback0::Type* work);
+  virtual void DoWorkAndWaitUntilDone(

[akalin, 2011/10/24 23:20:49]

It doesn't make sense to do the base class first and the derived class later
since you're changing the type signature.  That just means that all function
calls will go to this one and that'll break.

[lipalani1, 2011/10/25 02:29:46]

Done.

+    Callback1<sessions::UnrecoverableErrorInfo*>::Type* work,

[akalin, 2011/10/24 23:20:49]

the callbacktype should be ErrorInfo(void) (i.e., the work function should
return the struct directly)

[lipalani1, 2011/10/25 02:29:46]

As discussed we have to pass the pointer because it is in another thread..
On 2011/10/24 23:20:49, akalin wrote:

[akalin, 2011/10/25 03:20:06]

Actually, it's only CallDoWorkAndSignalTask (e.g.) that must take a pointer. 
The callback itself can return the struct directly.  To clarify, it'll look like
this:

PostTask(..., CallDoWorkAndSIgnalTask(done, event, &error_info));

....

void CallDoWorkAndSignalTask(Callback1 ... done, ..., ErrorInfo* error_info) {
  *error_info = done->Run();
  Signal();
}

To put it in another way, you don't want the fact that some subclasses of
ModelSafeWorker posts on other threads to leak into the ModelSafeWorker
interface.

+    sessions::UnrecoverableErrorInfo* error_info);

[akalin, 2011/10/24 23:20:49]

make this return the ErrorInfo class directly

[lipalani1, 2011/10/25 02:29:46]

Done.

 
   virtual ModelSafeGroup GetModelSafeGroup();