Wait for URLBlacklist update tasks on automation tests.

content/browser/browser_thread.h

Index: content/browser/browser_thread.h
diff --git a/content/browser/browser_thread.h b/content/browser/browser_thread.h
index 2e798973bc8f6b532fda69eaf96aa4c659c94d62..f09fc6eb69cca3683a5b4eea3d3843ea949c4310 100644
--- a/content/browser/browser_thread.h
+++ b/content/browser/browser_thread.h
@@ -168,6 +168,13 @@ class CONTENT_EXPORT BrowserThread : public base::Thread {
   // sets identifier to its ID.  Otherwise returns false.
   static bool GetCurrentThreadIdentifier(ID* identifier);
 
+  // Runs all the current pending tasks on the given thread's message loop.
+  // This call blocks until those tasks are executed, effectively making the
+  // current thread block on |identifier|. Avoid using this.
+  // Returns false if |identifier| is the current thread, or a task couldn't be
+  // posted to |identifier|'s message loop.
+  static bool WaitForPendingTasksOn(ID identifier);

[jam, 2011/10/14 17:19:30]

this is most certainly a function that we don't want on BrowserThread. any such
function, once it's in, would be misused.

check out http://dev.chromium.org/developers/design-documents/threading

"Chromium is a very multithreaded product. We try to keep the UI as responsive
as possible, and this means not blocking the UI thread with any blocking I/O or
other expensive operations. Our approach is to use message passing as the way of
communicating between threads. We discourage locking and threadsafe objects.
Instead, objects live on only one thread, we pass messages between threads for
communication, and we use callback interfaces (implemented by message passing)
for most cross-thread requests."


I don't know the details of the test that you're trying to fix, but it seems
that you can do this waiting in the test code yourself, without touching the
content code.

+
   // Callers can hold on to a refcounted MessageLoopProxy beyond the lifetime
   // of the thread.
   static scoped_refptr<base::MessageLoopProxy> GetMessageLoopProxyForThread(