Added asynchronous notification of readiness to the StatisticsProvider, and

chrome/browser/chromeos/system/statistics_provider.h

Index: chrome/browser/chromeos/system/statistics_provider.h
diff --git a/chrome/browser/chromeos/system/statistics_provider.h b/chrome/browser/chromeos/system/statistics_provider.h
index 1908087826ccb6b91d74b66b56b69ea3cdbde80e..d76b63e291324697f54fe84e973633ceb29b4856 100644
--- a/chrome/browser/chromeos/system/statistics_provider.h
+++ b/chrome/browser/chromeos/system/statistics_provider.h
@@ -8,6 +8,8 @@
 
 #include <string>
 
+#include "base/callback.h"
+
 namespace chromeos {
 namespace system {
 
@@ -15,11 +17,20 @@ namespace system {
 class StatisticsProvider {
  public:
   // Retrieve the named machine statistic (e.g. "hardware_class").
-  // This does not update the statistcs. If the |name| is not set, |result|
-  // preserves old value.
+  // This does not update the statistcs. |result| is not updated if |name| is
+  // not set.
+  // This call may block if the statistics aren't ready yet, up to a timeout;
+  // it may also fail because the statistics weren't ready before the timeout.
+  // To make sure this won't block nor fail, invoke GetMachineStatistic() after
+  // WhenReady() has invoked its callback.
   virtual bool GetMachineStatistic(const std::string& name,
                                    std::string* result) = 0;
 
+  // Invokes |callback| on the UI loop once the statistics have been loaded.
+  // |callback| is immediately posted to the UI loop if the statistics are
+  // already available.
+  virtual void WhenReady(const base::Closure& callback) = 0;
+
   static StatisticsProvider* GetInstance();
 
  protected: