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 f7b88ff1d3504bf5ea5f538d4e6a5ce5be6fbfdf..7d82cd0ddbd0582672291e8fbb2609e075cb7aa4 100644
--- a/chrome/browser/chromeos/system/statistics_provider.cc
+++ b/chrome/browser/chromeos/system/statistics_provider.cc
@@ -5,11 +5,14 @@
 #include "chrome/browser/chromeos/system/statistics_provider.h"
 
 #include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/chromeos/chromeos_version.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
+#include "base/message_loop.h"
+#include "base/metrics/histogram.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/time.h"
 #include "base/chromeos/chromeos_version.h"
@@ -62,6 +65,15 @@ const char kVpdDelim[] = "\n";
 // Timeout that we should wait for statistics to get loaded
 const int kTimeoutSecs = 3;
 
+// Helper to invoke |callbacks| on the UI thread.
+void NotifyOnUI(const std::vector<base::Closure>& callbacks) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  for (std::vector<base::Closure>::const_iterator it = callbacks.begin();
+       it != callbacks.end(); ++it) {
+    it->Run();
+  }
+}
+
 }  // namespace
 
 // The StatisticsProvider implementation used in production.
@@ -71,6 +83,8 @@ 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:
@@ -86,14 +100,16 @@ class StatisticsProviderImpl : public StatisticsProvider {
 
   NameValuePairsParser::NameValueMap machine_info_;
   base::WaitableEvent on_statistics_loaded_;
+  std::vector<base::Closure> callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(StatisticsProviderImpl);
 };
 
 bool StatisticsProviderImpl::GetMachineStatistic(
-    const std::string& name, std::string* result) {
+    const std::string& name,
+    std::string* result) {
   VLOG(1) << "Statistic is requested for " << name;
-  // Block if the statistics are not loaded yet. Per LOG(WARNING) below,
+  // Block if the statistics are not loaded yet. Per DLOG(WARNING) below,
   // the statistics are loaded before requested as of now. For regular
   // sessions (i.e. not OOBE), statistics are first requested when the
   // user is logging in so we have plenty of time to load the data
@@ -104,13 +120,13 @@ bool StatisticsProviderImpl::GetMachineStatistic(
   // very early stage of the browser startup. The statistic name should be
   // helpful to identify the caller.
   if (!on_statistics_loaded_.IsSignaled()) {
-    LOG(WARNING) << "Waiting to load statistics. Requested statistic: "
-                 << name;
+    DLOG(WARNING) << "Waiting to load statistics. Requested statistic: "
+                  << name;
     on_statistics_loaded_.TimedWait(base::TimeDelta::FromSeconds(kTimeoutSecs));
 
     if (!on_statistics_loaded_.IsSignaled()) {
-      LOG(ERROR) << "Statistics weren't loaded after waiting! "
-                 << "Requested statistic: " << name;
+      DLOG(ERROR) << "Statistics weren't loaded after waiting! "
+                  << "Requested statistic: " << name;
       return false;
     }
   }
@@ -123,6 +139,16 @@ 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 */,
@@ -145,8 +171,9 @@ void StatisticsProviderImpl::LoadMachineStatistics() {
   if (!parser.ParseNameValuePairsFromTool(
           arraysize(kCrosSystemTool), kCrosSystemTool, kCrosSystemEq,
           kCrosSystemDelim, kCrosSystemCommentDelim)) {
-    LOG(WARNING) << "There were errors parsing the output of "
-                 << kCrosSystemTool << ".";
+    DLOG(WARNING) << "There were errors parsing the output of "
+                  << kCrosSystemTool << ".";
+    UMA_HISTOGRAM_BOOLEAN("Cros.CrosSystemParsingFailed", true);
   }
 
   // Ensure that the hardware class key is present with the expected
@@ -172,6 +199,13 @@ 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(NotifyOnUI, callbacks_));
+  callbacks_.clear();
+
 #if defined(GOOGLE_CHROME_BUILD)
   // TODO(kochi): This is for providing a channel information to
   // chrome::VersionInfo::GetChannel()/GetVersionStringModifier(),
@@ -210,6 +244,11 @@ class StatisticsProviderStubImpl : public StatisticsProvider {
     return false;
   }
 
+  virtual void WhenReady(const base::Closure& callback) OVERRIDE {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
+  }
+
   static StatisticsProviderStubImpl* GetInstance() {
     return Singleton<StatisticsProviderStubImpl,
         DefaultSingletonTraits<StatisticsProviderStubImpl> >::get();