Added an integration test for kasko hang reports

components/browser_watcher/window_hang_monitor_win.cc

Index: components/browser_watcher/window_hang_monitor_win.cc
diff --git a/components/browser_watcher/window_hang_monitor_win.cc b/components/browser_watcher/window_hang_monitor_win.cc
index 964a6f76f4620a56aa2d2d4a557d1bec65b63ec5..c5a60b05c31dc8220508251efa80f2786712f8d7 100644
--- a/components/browser_watcher/window_hang_monitor_win.cc
+++ b/components/browser_watcher/window_hang_monitor_win.cc
@@ -13,13 +13,29 @@ namespace browser_watcher {
 
 namespace {
 
-HWND FindNamedWindowForProcess(const base::string16 name, base::ProcessId pid) {
-  HWND candidate = base::win::MessageWindow::FindWindow(name);
-  if (candidate) {
+// Returns the class name for the |window|.
+base::string16 GetWindowClassName(HWND window) {
+  const int kClassNameLength = MAX_PATH;
+  wchar_t class_name[kClassNameLength];
+  int nb_copied = ::GetClassName(window, class_name, kClassNameLength);
+  if (nb_copied) {
+    return base::string16(class_name);
+  }
+  return base::string16();
+}
+
+// Returns the Chrome message window handle for the specified |pid| or nullptr
+// if not found.
+HWND FindChromeMessageWindow(base::ProcessId pid) {

[Sigurður Ásgeirsson, 2016/01/11 19:42:59]

now that I think about it, I'm not sure this is "good enough". The problem is
that this will find *A* message window, but I don't know that there's precisely
zero or one of those per chrome instance. The lifetime of other message windows
may or may not be appropriate for hang monitoring.

[Patrick Monette, 2016/01/20 17:21:35]

So I'm now also check that the name of the window is an existing path.

+  HWND candidate = ::FindWindowEx(HWND_MESSAGE, nullptr, nullptr, nullptr);
+  while (candidate) {
     DWORD actual_process_id = 0;
     ::GetWindowThreadProcessId(candidate, &actual_process_id);
-    if (actual_process_id == pid)
+    if (GetWindowClassName(candidate) == L"Chrome_MessageWindow" &&

[Sigurður Ásgeirsson, 2016/01/11 19:42:59]

doesn't matter a whole lot, but you can avoid a bunch of string copying here by
naming this function something like IsWindowClassName, and passing it a
stringpiece.

[Patrick Monette, 2016/01/20 17:21:35]

Done.

+        actual_process_id == pid) {
       return candidate;
+    }
+    candidate = ::GetNextWindow(candidate, GW_HWNDNEXT);
   }
   return nullptr;
 }
@@ -45,9 +61,7 @@ WindowHangMonitor::~WindowHangMonitor() {
   }
 }
 
-void WindowHangMonitor::Initialize(base::Process process,
-                                   const base::string16& window_name) {
-  window_name_ = window_name;
+void WindowHangMonitor::Initialize(base::Process process) {
   window_process_ = process.Pass();
   timer_.SetTaskRunner(base::MessageLoop::current()->task_runner());
 
@@ -69,7 +83,7 @@ void WindowHangMonitor::PollForWindow() {
     return;
   }
 
-  HWND hwnd = FindNamedWindowForProcess(window_name_, window_process_.Pid());
+  HWND hwnd = FindChromeMessageWindow(window_process_.Pid());
   if (hwnd) {
     // Sends a ping and schedules a timeout task. Upon receiving a ping response
     // further pings will be scheduled ad infinitum. Will signal any failure now
@@ -129,8 +143,7 @@ void WindowHangMonitor::OnHangTimeout(HWND hwnd) {
     outstanding_ping_->monitor = NULL;
     outstanding_ping_ = NULL;
 
-    if (hwnd !=
-        FindNamedWindowForProcess(window_name_, window_process_.Pid())) {
+    if (hwnd != FindChromeMessageWindow(window_process_.Pid())) {
       // The window vanished.
       callback_.Run(WINDOW_VANISHED);
     } else {
@@ -155,7 +168,7 @@ void WindowHangMonitor::OnRetryTimeout() {
   //    process.
   // 2. The window handle might have been re-assigned to a different process
   //    at any point after we found it.
-  HWND hwnd = FindNamedWindowForProcess(window_name_, window_process_.Pid());
+  HWND hwnd = FindChromeMessageWindow(window_process_.Pid());
   if (hwnd)
     SendPing(hwnd);
   else