Added asynchronous notification of readiness to the StatisticsProvider, and

chrome/browser/chromeos/system/statistics_provider.cc

Index: chrome/browser/chromeos/system/statistics_provider.cc
diff --git a/chrome/browser/chromeos/system/statistics_provider.cc b/chrome/browser/chromeos/system/statistics_provider.cc
index 0d6798f8f6890f4ac82208f2c60eca24ffe59bfe..c93956cc6ecb6af6450a73a5f4213f59b7cc2297 100644
--- a/chrome/browser/chromeos/system/statistics_provider.cc
+++ b/chrome/browser/chromeos/system/statistics_provider.cc
@@ -10,6 +10,7 @@
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
+#include "base/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/time.h"
 #include "base/chromeos/chromeos_version.h"
@@ -71,6 +72,8 @@ class StatisticsProviderImpl : public StatisticsProvider {
   virtual bool GetMachineStatistic(const std::string& name,
                                    std::string* result) OVERRIDE;
 
+  virtual void WhenReady(const base::Closure& callback) OVERRIDE;
+
   static StatisticsProviderImpl* GetInstance();
 
  private:
@@ -84,8 +87,12 @@ class StatisticsProviderImpl : public StatisticsProvider {
   // Loads the machine statistcs by examining the system.
   void LoadMachineStatistics();
 
+  // Invokes all the callbacks.
+  void NotifyOnUI();
+
   NameValuePairsParser::NameValueMap machine_info_;
   base::WaitableEvent on_statistics_loaded_;
+  std::vector<base::Closure> callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(StatisticsProviderImpl);
 };
@@ -117,6 +124,16 @@ bool StatisticsProviderImpl::GetMachineStatistic(
   return false;
 }
 
+void StatisticsProviderImpl::WhenReady(const base::Closure& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (on_statistics_loaded_.IsSignaled()) {
+    // Don't assume the caller is re-entrant.
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
+  } else {
+    callbacks_.push_back(callback);
+  }
+}
+
 // manual_reset needs to be true, as we want to keep the signaled state.
 StatisticsProviderImpl::StatisticsProviderImpl()
     : on_statistics_loaded_(true  /* manual_reset */,
@@ -166,6 +183,13 @@ void StatisticsProviderImpl::LoadMachineStatistics() {
   on_statistics_loaded_.Signal();
   VLOG(1) << "Finished loading statistics";
 
+  // Any callbacks registed before Signal() are in |callbacks_|. Any registed
+  // after Signal() will be immediately posted. NotifyOnUI() posts the callbacks
+  // in |callbacks_| from the UI loop.
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&StatisticsProviderImpl::NotifyOnUI,
+                                     base::Unretained(this)));
+
 #if defined(GOOGLE_CHROME_BUILD)
   // TODO(kochi): This is for providing a channel information to
   // chrome::VersionInfo::GetChannel()/GetVersionStringModifier(),
@@ -190,6 +214,15 @@ void StatisticsProviderImpl::LoadMachineStatistics() {
 #endif
 }
 
+void StatisticsProviderImpl::NotifyOnUI() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  for (std::vector<base::Closure>::iterator it = callbacks_.begin();
+       it != callbacks_.end(); ++it) {
+    it->Run();
+  }
+  callbacks_.clear();
+}
+
 StatisticsProviderImpl* StatisticsProviderImpl::GetInstance() {
   return Singleton<StatisticsProviderImpl,
                    DefaultSingletonTraits<StatisticsProviderImpl> >::get();
@@ -204,6 +237,10 @@ class StatisticsProviderStubImpl : public StatisticsProvider {
     return false;
   }
 
+  virtual void WhenReady(const base::Closure& callback) OVERRIDE {
+    callback.Run();
+  }
+
   static StatisticsProviderStubImpl* GetInstance() {
     return Singleton<StatisticsProviderStubImpl,
         DefaultSingletonTraits<StatisticsProviderStubImpl> >::get();