Differential updates for components.

chrome/browser/component_updater/component_updater_service.cc

Index: chrome/browser/component_updater/component_updater_service.cc
diff --git a/chrome/browser/component_updater/component_updater_service.cc b/chrome/browser/component_updater/component_updater_service.cc
index f3eee77c204791f46acb13e813f98b5b3b1f8a6b..e0746bab4baaddc519aebf5ea085576ef36c2c58 100644
--- a/chrome/browser/component_updater/component_updater_service.cc
+++ b/chrome/browser/component_updater/component_updater_service.cc
@@ -10,8 +10,10 @@
 
 #include "base/at_exit.h"
 #include "base/bind.h"
+#include "base/compiler_specific.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
+#include "base/guid.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/stl_util.h"
@@ -19,13 +21,16 @@
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/sys_info.h"
 #include "base/timer.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/browser/component_updater/component_patcher.h"
 #include "chrome/browser/component_updater/component_unpacker.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_utility_messages.h"
 #include "chrome/common/chrome_version_info.h"
 #include "chrome/common/extensions/extension.h"
+#include "chrome/common/omaha_query_params/omaha_query_params.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/utility_process_host.h"
@@ -47,21 +52,26 @@ using extensions::Extension;
 // base::Bind() calls are not refcounted.
 
 namespace {
+
+typedef ComponentUpdateService::Configurator Config;
+
 // Manifest sources, from most important to least important.
 const CrxComponent::UrlSource kManifestSources[] = {
   CrxComponent::BANDAID,
   CrxComponent::CWS_PUBLIC,
-  CrxComponent::CWS_SANDBOX
+  CrxComponent::CWS_SANDBOX,
 };
 
 // Extends an omaha compatible update check url |query| string. Does
 // not mutate the string if it would be longer than |limit| chars.
 bool AddQueryString(const std::string& id,
                     const std::string& version,
+                    const std::string& fingerprint,
                     size_t limit,
                     std::string* query) {
   std::string additional =
-      base::StringPrintf("id=%s&v=%s&uc", id.c_str(), version.c_str());
+      base::StringPrintf("id=%s&v=%s&fp=%s&uc",
+                         id.c_str(), version.c_str(), fingerprint.c_str());
   additional = "x=" + net::EscapeQueryParamValue(additional, true);
   if ((additional.size() + query->size() + 1) > limit)
     return false;
@@ -163,34 +173,81 @@ void StartFetch(net::URLFetcher* fetcher,
   fetcher->Start();
 }
 
-// Returs true if the url request of |fetcher| was succesful.
+// Returns true if the url request of |fetcher| was succesful.
 bool FetchSuccess(const net::URLFetcher& fetcher) {
   return (fetcher.GetStatus().status() == net::URLRequestStatus::SUCCESS) &&
          (fetcher.GetResponseCode() == 200);
 }
 
+// Returns the error code which occured during the fetch. This function
+// is intended to be called for logging purposes only, since it folds different
+// types of errors to fit them in the returned type. The function returns 0 if
+// the fetch was successful. If errors happen, the function could return a
+// network error, an http response code, or the status of the fetch, if the
+// fetch is pending or canceled.
+int GetFetchError(const net::URLFetcher& fetcher) {
+  if (FetchSuccess(fetcher))
+    return 0;
+
+  const net::URLRequestStatus::Status status(fetcher.GetStatus().status());
+  if (status == net::URLRequestStatus::FAILED)
+    return fetcher.GetStatus().error();
+
+  if (status == net::URLRequestStatus::IO_PENDING ||
+      status == net::URLRequestStatus::CANCELED)
+    return status;
+
+  const int response_code(fetcher.GetResponseCode());
+  if (status == net::URLRequestStatus::SUCCESS && response_code != 200)
+    return response_code;
+
+  return -1;
+}
+
+
 // This is the one and only per-item state structure. Designed to be hosted
 // in a std::vector or a std::list. The two main members are |component|
 // which is supplied by the the component updater client and |status| which
 // is modified as the item is processed by the update pipeline. The expected
 // transition graph is:
-//                                error          error         error
-//              +--kNoUpdate<------<-------+------<------+------<------+
-//              |                          |             |             |
-//              V                  yes     |             |             |
-//  kNew --->kChecking-->[update?]----->kCanUpdate-->kDownloading-->kUpdating
-//              ^               |                                      |
-//              |               |no                                    |
-//              |--kUpToDate<---+                                      |
-//              |                                  success             |
-//              +--kUpdated<-------------------------------------------+
+//
+//                                 kNew
+//                                  |
+//                                  V
+//     +----------------------> kChecking -<---------+-----<-------+
+//     |                            |                |             |
+//     |                            V       no       |             |
+//  kNoUpdate                   [update?] ->---- kUpToDate     kUpdated
+//     ^                            |                              ^
+//     |                        yes |                              |
+//     |        diff=false          V                              |
+//     |          +-----------> kCanUpdate                         |
+//     |          |                 |                              |
+//     |          |                 V              no              |
+//     |          |        [differential update?]->----+           |
+//     |          |                 |                  |           |
+//     |          |             yes |                  |           |
+//     |          |   error         V                  |           |
+//     |          +---------<- kDownloadingDiff        |           |
+//     |          |                 |                  |           |
+//     |          |                 |                  |           |
+//     |          |   error         V                  |           |
+//     |          +---------<- kUpdatingDiff ->--------|-----------+ success
+//     |                                               |           |
+//     |              error                            V           |
+//     +----------------------------------------- kDownloading     |
+//     |                                               |           |
+//     |              error                            V           |
+//     +------------------------------------------ kUpdating ->----+ success
 //
 struct CrxUpdateItem {
   enum Status {
     kNew,
     kChecking,
     kCanUpdate,
+    kDownloadingDiff,
     kDownloading,
+    kUpdatingDiff,
     kUpdating,
     kUpdated,
     kUpToDate,
@@ -199,13 +256,55 @@ struct CrxUpdateItem {
   };
 
   Status status;
-  GURL crx_url;
   std::string id;
-  base::Time last_check;
   CrxComponent component;
-  Version next_version;
 
-  CrxUpdateItem() : status(kNew) {}
+  base::Time last_check;
+
+  // True if the update response includes an update for this component.
+  bool is_update_available;
+
+  // True is a completion ping has been queued for this component. If an update
+  // is available for this component, one completion ping must be sent
+  // after the component has reached either the kNoUpdate or kUpdated states.
+  bool ping_queued;
+
+  // These members are initialized with their corresponding values from the
+  // update server response.
+  GURL crx_url;
+  GURL diff_crx_url;
+  std::string package_hash;
+  std::string diff_package_hash;
+  int size;
+  int diff_size;
+
+  // The from/to version and fingerprint values.
+  Version previous_version;
+  Version next_version;
+  std::string previous_fp;
+  std::string next_fp;
+
+  // True if the differential update failed for any reason.
+  bool diff_update_failed;
+
+  // The error information for full and differential updates.
+  int error_code;
+  int extra_code1;
+  int diff_error_code;
+  int diff_extra_code1;
+
+  CrxUpdateItem()
+      : status(kNew),
+        is_update_available(false),
+        ping_queued(false),
+        size(0),
+        diff_size(0),
+        diff_update_failed(false),
+        error_code(0),
+        extra_code1(0),
+        diff_error_code(0),
+        diff_extra_code1(0) {
+  }
 
   // Function object used to find a specific component.
   class FindById {
@@ -220,9 +319,20 @@ struct CrxUpdateItem {
   };
 };
 
-}  // namespace.
+// Returns true if a differential update is available for the update item.
+bool IsDiffUpdateAvailable(const CrxUpdateItem* update_item) {
+  return update_item->diff_crx_url.is_valid();
+}
 
-typedef ComponentUpdateService::Configurator Config;
+// Returns true if a differential update is available, it has not failed yet,
+// and the configuration allows it.
+bool CanTryDiffUpdate(const CrxUpdateItem* update_item, const Config& config) {
+  return IsDiffUpdateAvailable(update_item) &&
+         !update_item->diff_update_failed &&
+         config.DeltasEnabled();
+}
+
+}  // namespace.
 
 CrxComponent::CrxComponent()
     : installer(NULL),
@@ -240,7 +350,7 @@ CrxComponent::~CrxComponent() {
 // rest of the browser, so even if we have many components registered and
 // eligible for update, we only do one thing at a time with pauses in between
 // the tasks. Also when we do network requests there is only one |url_fetcher_|
-// in flight at at a time.
+// in flight at a time.
 // There are no locks in this code, the main structure |work_items_| is mutated
 // only from the UI thread. The unpack and installation is done in the file
 // thread and the network requests are done in the IO thread and in the file
@@ -299,11 +409,16 @@ class CrxUpdateService : public ComponentUpdateService {
     UpdateContext() : start(base::Time::Now()) {}
   };
 
+  // Context for a completion ping.
+  struct PingContext {

[robertshield, 2013/06/17 17:47:00]

This struct appears rather empty. If it's here as a placeholder for future work,
please add a comment to that effect.

[Sorin Jianu, 2013/06/17 22:21:09]

Done.

+  };
+
   // Context for a crx download url request. See DelegateWithContext above.
   struct CRXContext {
     ComponentInstaller* installer;
     std::vector<uint8> pk_hash;
     std::string id;
+    std::string fingerprint;
     CRXContext() : installer(NULL) {}
   };
 
@@ -313,14 +428,16 @@ class CrxUpdateService : public ComponentUpdateService {
   void OnURLFetchComplete(const net::URLFetcher* source,
                           CRXContext* context);
 
+  void OnURLFetchComplete(const net::URLFetcher* source,
+                          PingContext* context);
+
  private:
   // See ManifestParserBridge.
   void OnParseUpdateManifestSucceeded(
       const UpdateManifest::Results& results);
 
   // See ManifestParserBridge.
-  void OnParseUpdateManifestFailed(
-      const std::string& error_message);
+  void OnParseUpdateManifestFailed(const std::string& error_message);
 
   bool AddItemToUpdateCheck(CrxUpdateItem* item, std::string* query);
 
@@ -333,19 +450,33 @@ class CrxUpdateService : public ComponentUpdateService {
   void Install(const CRXContext* context, const base::FilePath& crx_path);
 
   void DoneInstalling(const std::string& component_id,
-                      ComponentUnpacker::Error error);
+                      ComponentUnpacker::Error error,
+                      int extended_error);
 
   size_t ChangeItemStatus(CrxUpdateItem::Status from,
                           CrxUpdateItem::Status to);
 
   CrxUpdateItem* FindUpdateItemById(const std::string& id);
 
+  void SendPing(const std::string& ping);
+
+  // These functions build a ping request. Building the ping changes the state
+  // of the update item to indicate that a completion ping has been collected
+  // and queued for this item.
+  std::string BuildPing() const;
+  std::string BuildPingApps() const;
+  static std::string BuildPingEvent(CrxUpdateItem* item);
+
   scoped_ptr<Config> config_;
 
+  scoped_ptr<ComponentPatcher> component_patcher_;
+
   scoped_ptr<net::URLFetcher> url_fetcher_;
 
-  typedef std::vector<CrxUpdateItem*> UpdateItems;
+  scoped_ptr<net::URLFetcher> ping_sender_;
+
   // A collection of every work item.
+  typedef std::vector<CrxUpdateItem*> UpdateItems;
   UpdateItems work_items_;
 
   // A particular set of items from work_items_, which should be checked ASAP.
@@ -353,7 +484,10 @@ class CrxUpdateService : public ComponentUpdateService {
 
   base::OneShotTimer<CrxUpdateService> timer_;
 
-  Version chrome_version_;
+  const Version chrome_version_;
+  const std::string prod_id_;
+  const std::string os_type_;
+  const std::string os_version_;
 
   bool running_;
 
@@ -362,10 +496,14 @@ class CrxUpdateService : public ComponentUpdateService {
 
 //////////////////////////////////////////////////////////////////////////////
 
-CrxUpdateService::CrxUpdateService(
-    ComponentUpdateService::Configurator* config)
+CrxUpdateService::CrxUpdateService(ComponentUpdateService::Configurator* config)
     : config_(config),
+      component_patcher_(config->CreateComponentPatcher()),
       chrome_version_(chrome::VersionInfo().Version()),
+      prod_id_(chrome::OmahaQueryParams::GetProdIdString(
+          chrome::OmahaQueryParams::CHROME)),
+      os_type_(chrome::VersionInfo().OSType()),
+      os_version_(base::SysInfo().OperatingSystemVersion()),
       running_(false) {
 }
 
@@ -418,6 +556,12 @@ void CrxUpdateService::ScheduleNextRun(bool step_delay) {
   if (!running_)
     return;
 
+  if (!step_delay && config_->PingsEnabled()) {
+    const std::string ping(BuildPing());
+    if (!ping.empty())
+      SendPing(ping);
+  }
+
   // Keep the delay short if in the middle of an update (step_delay),
   // or there are new requested_work_items_ that have not been processed yet.
   int64 delay = (step_delay || requested_work_items_.size() > 0)
@@ -491,6 +635,7 @@ ComponentUpdateService::Status CrxUpdateService::RegisterComponent(
   uit = new CrxUpdateItem;
   uit->id.swap(id);
   uit->component = component;
+
   work_items_.push_back(uit);
   // If this is the first component registered we call Start to
   // schedule the first timer.
@@ -508,10 +653,23 @@ bool CrxUpdateService::AddItemToUpdateCheck(CrxUpdateItem* item,
                                             std::string* query) {
   if (!AddQueryString(item->id,
                       item->component.version.GetString(),
+                      item->component.fingerprint,
                       config_->UrlSizeLimit(), query))
     return false;
+
   item->status = CrxUpdateItem::kChecking;
   item->last_check = base::Time::Now();
+  item->is_update_available = false;
+  item->ping_queued = false;
+  item->previous_version = item->component.version;
+  item->next_version = Version();
+  item->previous_fp = item->component.fingerprint;
+  item->next_fp = "";
+  item->diff_update_failed = false;
+  item->error_code = 0;
+  item->extra_code1 = 0;
+  item->diff_error_code = 0;
+  item->diff_extra_code1 = 0;
   return true;
 }
 
@@ -535,16 +693,17 @@ ComponentUpdateService::Status CrxUpdateService::CheckForUpdateSoon(
 
   // Check if the request is too soon.
   base::TimeDelta delta = base::Time::Now() - uit->last_check;
-  if (delta < base::TimeDelta::FromSeconds(config_->OnDemandDelay())) {
+  if (delta < base::TimeDelta::FromSeconds(config_->OnDemandDelay()))
     return kError;
-  }
 
   switch (uit->status) {
     // If the item is already in the process of being updated, there is
     // no point in this call, so return kInProgress.
     case CrxUpdateItem::kChecking:
     case CrxUpdateItem::kCanUpdate:
+    case CrxUpdateItem::kDownloadingDiff:
     case CrxUpdateItem::kDownloading:
+    case CrxUpdateItem::kUpdatingDiff:
     case CrxUpdateItem::kUpdating:
       return kInProgress;
     // Otherwise the item was already checked a while back (or it is new),
@@ -583,13 +742,21 @@ void CrxUpdateService::ProcessPendingItems() {
     if (item->status != CrxUpdateItem::kCanUpdate)
       continue;
     // Found component to update, start the process.
-    item->status = CrxUpdateItem::kDownloading;
     CRXContext* context = new CRXContext;
     context->pk_hash = item->component.pk_hash;
     context->id = item->id;
     context->installer = item->component.installer;
+    context->fingerprint = item->next_fp;
+    GURL package_url;
+    if (CanTryDiffUpdate(item, *config_)) {
+      package_url = item->diff_crx_url;
+      item->status = CrxUpdateItem::kDownloadingDiff;
+    } else {
+      package_url = item->crx_url;
+      item->status = CrxUpdateItem::kDownloading;
+    }
     url_fetcher_.reset(net::URLFetcher::Create(
-        0, item->crx_url, net::URLFetcher::GET,
+        0, package_url, net::URLFetcher::GET,
         MakeContextDelegate(this, context)));
     StartFetch(url_fetcher_.get(), config_->RequestContext(), true);
     return;
@@ -700,11 +867,10 @@ void CrxUpdateService::ParseManifest(const std::string& xml) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   if (config_->InProcess()) {
     UpdateManifest manifest;
-    if (!manifest.Parse(xml)) {
+    if (!manifest.Parse(xml))
        CrxUpdateService::OnParseUpdateManifestFailed(manifest.errors());
-    } else {
+    else
        CrxUpdateService::OnParseUpdateManifestSucceeded(manifest.results());
-    }
   } else {
     UtilityProcessHost* host =
         UtilityProcessHost::Create(new ManifestParserBridge(this),
@@ -752,9 +918,16 @@ void CrxUpdateService::OnParseUpdateManifestSucceeded(
     }
     // All test passed. Queue an upgrade for this component and fire the
     // notifications.
+    crx->is_update_available = true;
     crx->crx_url = it->crx_url;
+    crx->package_hash = it->package_hash;
+    crx->size = it->size;
+    crx->diff_crx_url = it->diff_crx_url;
+    crx->diff_package_hash = it->diff_package_hash;
+    crx->diff_size = it->diff_size;
     crx->status = CrxUpdateItem::kCanUpdate;
     crx->next_version = Version(it->version);
+    crx->next_fp = it->package_fingerprint;
     ++update_pending;
 
     content::NotificationService::current()->Notify(
@@ -789,19 +962,31 @@ void CrxUpdateService::OnURLFetchComplete(const net::URLFetcher* source,
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   int error_code = net::OK;
 
+  CrxUpdateItem* crx = FindUpdateItemById(context->id);
+
   if (source->FileErrorOccurred(&error_code) || !FetchSuccess(*source)) {
-    size_t count = ChangeItemStatus(CrxUpdateItem::kDownloading,
-                                    CrxUpdateItem::kNoUpdate);
-    DCHECK_EQ(count, 1ul);
+    if (crx->status == CrxUpdateItem::kDownloadingDiff) {
+      crx->diff_error_code = GetFetchError(*source);
+      crx->diff_update_failed = true;
+      crx->status = CrxUpdateItem::kCanUpdate;
+      BrowserThread::PostTask(
+          BrowserThread::UI,
+          FROM_HERE,
+          base::Bind(&CrxUpdateService::ProcessPendingItems,
+                     base::Unretained(this)));
+      return;
+    }
+    crx->error_code = GetFetchError(*source);
+    crx->status = CrxUpdateItem::kNoUpdate;
     config_->OnEvent(Configurator::kNetworkError, CrxIdtoUMAId(context->id));
     url_fetcher_.reset();
     ScheduleNextRun(false);
   } else {
     base::FilePath temp_crx_path;
     CHECK(source->GetResponseAsFilePath(true, &temp_crx_path));
-    size_t count = ChangeItemStatus(CrxUpdateItem::kDownloading,
-                                    CrxUpdateItem::kUpdating);
-    DCHECK_EQ(count, 1ul);
+    crx->status = (crx->status == CrxUpdateItem::kDownloadingDiff) ?
+        CrxUpdateItem::kUpdatingDiff : CrxUpdateItem::kUpdating;
+
     url_fetcher_.reset();
 
     content::NotificationService::current()->Notify(
@@ -829,17 +1014,19 @@ void CrxUpdateService::Install(const CRXContext* context,
                                const base::FilePath& crx_path) {
   // This function owns the |crx_path| and the |context| object.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  ComponentUnpacker
-      unpacker(context->pk_hash, crx_path, context->installer);
-  if (!file_util::Delete(crx_path, false)) {
+  ComponentUnpacker unpacker(context->pk_hash,
+                             crx_path,
+                             context->fingerprint,
+                             component_patcher_.get(),
+                             context->installer);
+  if (!file_util::Delete(crx_path, false))
     NOTREACHED() << crx_path.value();
-  }
   // Why unretained? See comment at top of file.
   BrowserThread::PostDelayedTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(&CrxUpdateService::DoneInstalling, base::Unretained(this),
-                 context->id, unpacker.error()),
+                 context->id, unpacker.error(), unpacker.extended_error()),
       base::TimeDelta::FromMilliseconds(config_->StepDelay()));
   delete context;
 }
@@ -847,14 +1034,37 @@ void CrxUpdateService::Install(const CRXContext* context,
 // Installation has been completed. Adjust the component status and
 // schedule the next check.
 void CrxUpdateService::DoneInstalling(const std::string& component_id,
-                                      ComponentUnpacker::Error error) {
+                                      ComponentUnpacker::Error error,
+                                      int extra_code) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   CrxUpdateItem* item = FindUpdateItemById(component_id);
+  if (item->status == CrxUpdateItem::kUpdatingDiff) {
+    if (error != ComponentUnpacker::kNone) {
+      item->diff_error_code = error;
+      item->diff_extra_code1 = extra_code;
+      item->diff_update_failed = true;
+      item->status = CrxUpdateItem::kCanUpdate;
+      BrowserThread::PostTask(
+          BrowserThread::UI,
+          FROM_HERE,
+          base::Bind(&CrxUpdateService::ProcessPendingItems,
+                     base::Unretained(this)));
+      return;
+    }
+  }
+
+  if (error != ComponentUnpacker::kNone) {
+    item->error_code = error;
+    item->extra_code1 = extra_code;
+  }
+
   item->status = (error == ComponentUnpacker::kNone) ? CrxUpdateItem::kUpdated :
                                                        CrxUpdateItem::kNoUpdate;
-  if (item->status == CrxUpdateItem::kUpdated)
+  if (item->status == CrxUpdateItem::kUpdated) {
     item->component.version = item->next_version;
+    item->component.fingerprint = item->next_fp;
+  }
 
   Configurator::Events event;
   switch (error) {
@@ -873,6 +1083,108 @@ void CrxUpdateService::DoneInstalling(const std::string& component_id,
   ScheduleNextRun(false);
 }
 
+void CrxUpdateService::SendPing(const std::string& ping) {
+  VLOG(3) << "Sending ping. " << ping;
+  const std::string ping_url(config_->PingUrl().spec());
+  ping_sender_.reset(net::URLFetcher::Create(
+      0, GURL(ping_url), net::URLFetcher::POST,
+      MakeContextDelegate(this, new PingContext())));
+  ping_sender_->SetUploadData(std::string("application/xml"), ping);
+  StartFetch(ping_sender_.get(), config_->RequestContext(), false);
+}
+
+void CrxUpdateService::OnURLFetchComplete(const net::URLFetcher* source,
+                                          PingContext* context) {
+  VLOG(3) << "Sending component update ping returned "
+          << FetchSuccess(*source);
+  ping_sender_.reset();
+}
+
+// Builds a ping message for the update items that have completed. Returns
+// an empty string if there are no completed items.
+std::string CrxUpdateService::BuildPing() const {
+  const std::string apps(BuildPingApps());
+  if (apps.empty())
+    return std::string();
+
+  const char response_format[] =
+      "<o:gupdate xmlns:o=\"http://www.google.com/update2/request\" "
+      "protocol=\"2.0\" version=\"%s-%s\" requestid=\"{%s}\"> "
+      "<o:os platform=\"%s\" version=\"%s\"/> "
+      "%s"
+      "</o:gupdate>";
+  const std::string response_envelope(
+      base::StringPrintf(response_format,
+                         prod_id_.c_str(),
+                         chrome_version_.GetString().c_str(),
+                         base::GenerateGUID().c_str(),
+                         os_type_.c_str(),
+                         os_version_.c_str(),
+                         apps.c_str()));
+  return response_envelope;
+}
+
+// Returns a string containing the sequence of app elements inside the
+// ping message.
+std::string CrxUpdateService::BuildPingApps() const {
+  const char app_format[] = "<o:app appid=\"%s\" version=\"%s\">%s</o:app>";
+
+  std::string ping_apps;
+  for (UpdateItems::const_iterator it = work_items_.begin();
+       it != work_items_.end(); ++it) {
+    CrxUpdateItem* item = *it;
+    // Only ping once if an update was available and the item is completed.
+    if (item->is_update_available && !item->ping_queued &&
+        (item->status == CrxUpdateItem::kNoUpdate ||
+         item->status == CrxUpdateItem::kUpdated)) {
+      const std::string version = item->component.version.GetString().c_str();
+      ping_apps += base::StringPrintf(app_format,
+                                      item->id.c_str(),
+                                      version.c_str(),
+                                      BuildPingEvent(item).c_str());
+    }
+  }
+  return ping_apps;
+}
+
+// Returns a string representing one ping event for an update item.
+std::string CrxUpdateService::BuildPingEvent(CrxUpdateItem* item) {
+  DCHECK(item->status == CrxUpdateItem::kNoUpdate ||
+         item->status == CrxUpdateItem::kUpdated);
+  DCHECK(item->is_update_available);
+
+  using base::StringAppendF;
+
+  std::string ping_event("<o:event eventtype=\"3\"");
+  const int event_result = item->status == CrxUpdateItem::kUpdated;
+  StringAppendF(&ping_event, " eventresult=\"%d\"", event_result);
+  StringAppendF(&ping_event, " previousversion=\"%s\"",
+                item->previous_version.GetString().c_str());
+  StringAppendF(&ping_event, " nextversion=\"%s\"",
+                item->next_version.GetString().c_str());
+  if (item->error_code)
+    StringAppendF(&ping_event, " errorcode=\"%d\"", item->error_code);
+  if (item->extra_code1)
+    StringAppendF(&ping_event, " extracode1=\"%d\"", item->extra_code1);
+  if (IsDiffUpdateAvailable(item))
+    StringAppendF(&ping_event, " diffresult=\"%d\"", !item->diff_update_failed);
+  if (item->diff_error_code)
+    StringAppendF(&ping_event, " differrorcode=\"%d\"", item->diff_error_code);
+  if (item->diff_extra_code1) {
+    StringAppendF(&ping_event,
+                  " diffextracode1=\"%d\"",
+                  item->diff_extra_code1);
+  }
+  if (!item->previous_fp.empty())
+    StringAppendF(&ping_event, " previousfp=\"%s\"", item->previous_fp.c_str());
+  if (!item->next_fp.empty())
+    StringAppendF(&ping_event, " nextfp=\"%s\"", item->next_fp.c_str());
+  StringAppendF(&ping_event, "/>");
+  item->ping_queued = true;
+  return ping_event;
+}
+
+
 // The component update factory. Using the component updater as a singleton
 // is the job of the browser process.
 ComponentUpdateService* ComponentUpdateServiceFactory(