Fix assertion starting cast_shell (breaking thread IO restrictions).

ui/events/ozone/device/device_manager_manual.cc

Index: ui/events/ozone/device/device_manager_manual.cc
diff --git a/ui/events/ozone/device/device_manager_manual.cc b/ui/events/ozone/device/device_manager_manual.cc
index c86ffccf62bdae50079e2927d77841a24cefdc7d..f5e1eca3e4e9c3b20060ee93ab12dc57ce30e5e2 100644
--- a/ui/events/ozone/device/device_manager_manual.cc
+++ b/ui/events/ozone/device/device_manager_manual.cc
@@ -4,30 +4,71 @@
 
 #include "ui/events/ozone/device/device_manager_manual.h"
 
+#include "base/bind.h"
+#include "base/callback.h"
 #include "base/files/file_enumerator.h"
+#include "base/location.h"
+#include "base/threading/worker_pool.h"
 #include "ui/events/ozone/device/device_event.h"
 #include "ui/events/ozone/device/device_event_observer.h"
 
 namespace ui {
 
-DeviceManagerManual::DeviceManagerManual() {}
+namespace {
 
-DeviceManagerManual::~DeviceManagerManual() {}
-
-void DeviceManagerManual::ScanDevices(DeviceEventObserver* observer) {
+void ScanDevicesOnWorkerThread(std::vector<base::FilePath>* result) {
   base::FileEnumerator file_enum(base::FilePath("/dev/input"),
                                  false,
                                  base::FileEnumerator::FILES,
                                  "event*[0-9]");
   for (base::FilePath path = file_enum.Next(); !path.empty();
        path = file_enum.Next()) {
-    DeviceEvent event(DeviceEvent::INPUT, DeviceEvent::ADD, path);
-    observer->OnDeviceEvent(event);
+    result->push_back(path);
+  }
+}
+}
+
+DeviceManagerManual::DeviceManagerManual()
+    : have_scanned_devices_(false), weak_ptr_factory_(this) {
+}
+
+DeviceManagerManual::~DeviceManagerManual() {
+}
+
+void DeviceManagerManual::ScanDevices(DeviceEventObserver* observer) {
+  if (have_scanned_devices_) {

[dnicoara, 2015/01/22 22:38:57]

Drive-by comment: If multiple callers end up scanning before the worker task
returns, there will be multiple calls to OnDevicesScanned, right? You'll need to
diff between the stored list and the new list otherwise all the devices that
appear in both lists will be duplicates. (Or maybe just discard the old list.)

I wonder if it's worth dropping |have_scanned_devices_| and always posting the
call to ScanDevicesOnWorkerThread()?

[spang, 2015/01/22 22:42:02]

have_scanned_devices_ is set here in this function, not after the scan
completes. It is not possible to kick off a 2nd scan.

[dnicoara, 2015/01/22 22:43:13]

Oh, sorry, didn't notice it. Sorry for the noise.

+    std::vector<base::FilePath>::const_iterator it = devices_.begin();
+    for (; it != devices_.end(); ++it) {
+      DeviceEvent event(DeviceEvent::INPUT, DeviceEvent::ADD, *it);
+      observer->OnDeviceEvent(event);
+    }
+  } else {
+    std::vector<base::FilePath>* result = new std::vector<base::FilePath>();
+    base::WorkerPool::PostTaskAndReply(
+        FROM_HERE, base::Bind(&ScanDevicesOnWorkerThread, result),
+        base::Bind(&DeviceManagerManual::OnDevicesScanned,
+                   weak_ptr_factory_.GetWeakPtr(), base::Owned(result)),
+        false /* task_is_slow */);
+    have_scanned_devices_ = true;
   }
 }
 
-void DeviceManagerManual::AddObserver(DeviceEventObserver* observer) {}
+void DeviceManagerManual::AddObserver(DeviceEventObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void DeviceManagerManual::RemoveObserver(DeviceEventObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
 
-void DeviceManagerManual::RemoveObserver(DeviceEventObserver* observer) {}
+void DeviceManagerManual::OnDevicesScanned(
+    std::vector<base::FilePath>* result) {
+  std::vector<base::FilePath>::const_iterator it = result->begin();
+  for (; it != result->end(); ++it) {
+    devices_.push_back(*it);
+    DeviceEvent event(DeviceEvent::INPUT, DeviceEvent::ADD, *it);
+    FOR_EACH_OBSERVER(DeviceEventObserver, observers_, OnDeviceEvent(event));
+  }
+}
 
 }  // namespace ui