[Media Gallery] Added code to support mtp device media file system on Windows.

chrome/browser/system_monitor/portable_device_watcher_win.cc

Index: chrome/browser/system_monitor/portable_device_watcher_win.cc
diff --git a/chrome/browser/system_monitor/portable_device_watcher_win.cc b/chrome/browser/system_monitor/portable_device_watcher_win.cc
index bd326adf79082383620880e8088a759349fe8ef4..d7eca1703881234434c78f3a1e24294ab2655618 100644
--- a/chrome/browser/system_monitor/portable_device_watcher_win.cc
+++ b/chrome/browser/system_monitor/portable_device_watcher_win.cc
@@ -516,6 +516,33 @@ void PortableDeviceWatcherWin::OnWindowMessage(UINT event_type, LPARAM data) {
     HandleDeviceDetachEvent(device_id);
 }
 
+bool PortableDeviceWatcherWin::GetMTPStorageInfoFromDeviceId(
+    const std::string& storage_device_id,
+    string16* device_location,
+    string16* storage_object_id) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  DCHECK(device_location);
+  DCHECK(storage_object_id);
+  MTPStorageMap::const_iterator storage_map_iter =
+      storage_map_.find(storage_device_id);
+  if (storage_map_iter == storage_map_.end())
+    return false;
+
+  *device_location = storage_map_iter->second.location;
+  MTPDeviceMap::const_iterator device_iter = device_map_.find(*device_location);
+  DCHECK(device_iter != device_map_.end());

[Ryan Sleevi, 2013/01/09 20:22:25]

This DCHECK leaves me a lil squicky, since AIUI, this API will ultimately be
glued up to client code and, given the threading, I find it very hard to reason
that this will always be the case (especially if the user removes devices etc)

Should this just be a proper check
if (device_iter == device_map_.end())
  return false;

[kmadhusu, 2013/01/10 04:59:19]

When the device is removed, line 528 will be true and we will do an early
return. To be safe, modified the DCHECK to a proper check.

+  const StorageObjects& storage_objects = device_iter->second;
+  for (StorageObjects::const_iterator storage_object_iter =
+       storage_objects.begin(); storage_object_iter != storage_objects.end();
+       ++storage_object_iter) {
+    if (storage_device_id == storage_object_iter->object_persistent_id) {
+      *storage_object_id = storage_object_iter->object_temporary_id;
+      break;
+    }
+  }
+  return !storage_object_id->empty();
+}
+
 void PortableDeviceWatcherWin::EnumerateAttachedDevices() {
   DCHECK(media_task_runner_.get());
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));