Merge m-c to birch

hal/gonk/GonkDiskSpaceWatcher.cpp

@@ -232,8 +232,13 @@ GonkDiskSpaceWatcher::OnFileCanReadWithoutBlocking(int aFd)
     len = read(aFd, buf, sizeof(buf));
   } while(len == -1 && errno == EINTR);
 
+  // Bail out if the file is busy.
+  if (len < 0 && errno == ETXTBSY) {
+    return;
+  }
+
   // We should get an exact multiple of fanotify_event_metadata
-  if (len <= 0 || (len % sizeof(*fem) != 0)) {
+  if (len <= 0 || (len % FAN_EVENT_METADATA_LEN != 0)) {
     printf_stderr("About to crash: fanotify_event_metadata read error.");
     MOZ_CRASH();
   }