Prefix match CHROMEOS_RELEASE_BOARD for checking chromebox.

It used to conatin only "stumpy", but recently official image contains
some suffix, and looks like "stumpy-signed-mp-v2keys". That change caused
regression, and this should fix it.

BUG=chromium:126732
TEST=Open some tabs on stumpy and sync, then on the other machine you should see "Chromebox" instead of "Chromebook" in "ohter devices" menu in new tab page.


Review URL: https://chromiumcodereview.appspot.com/10836257

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151839 0039d316-1c4b-4281-b951-d872f2087c98

sync/util/get_session_name.cc

@@ -30,16 +30,18 @@ namespace {
 std::string GetSessionNameSynchronously() {
   std::string session_name;
 #if defined(OS_CHROMEOS)
-  // TODO(kochi): This is very ad hoc and fragile. http://crosbug.com/30619.
+  // TODO(kochi): This is very ad hoc and fragile. http://crbug.com/126732.
   std::string board;
   const char kMachineInfoBoard[] = "CHROMEOS_RELEASE_BOARD";
   chromeos::system::StatisticsProvider* provider =
       chromeos::system::StatisticsProvider::GetInstance();
   if (!provider->GetMachineStatistic(kMachineInfoBoard, &board))
     LOG(ERROR) << "Failed to get board information";
   // Currently, only "stumpy" type of board is considered Chromebox, and
-  // anything else is Chromebook.
-  session_name = (board == "stumpy") ? "Chromebox" : "Chromebook";
+  // anything else is Chromebook.  On these devices, session_name should look
+  // like "stumpy-signed-mp-v2keys" etc. The information can be checked on
+  // "CHROMEOS_RELEASE_BOARD" line in chrome://system.
+  session_name = board.substr(0, 6) == "stumpy" ? "Chromebox" : "Chromebook";
 #elif defined(OS_LINUX)
   session_name = base::GetLinuxDistro();
 #elif defined(OS_MACOSX)