linux components: expose more BASE_API used by Chrome itself

base/global_descriptors_posix.h

Index: base/global_descriptors_posix.h
diff --git a/base/global_descriptors_posix.h b/base/global_descriptors_posix.h
index d635cff59f62bfa5a5217fe485941da21f76fbd3..d4650e50e7b0a39cebd36218d0310e5fc6c5bae9 100644
--- a/base/global_descriptors_posix.h
+++ b/base/global_descriptors_posix.h
@@ -34,7 +34,7 @@ namespace base {
 // It maps from an abstract key to a descriptor. If independent modules each
 // need to define keys, then values should be chosen randomly so as not to
 // collide.
-class GlobalDescriptors {
+class BASE_API GlobalDescriptors {
  public:
   typedef uint32_t Key;
   typedef std::vector<std::pair<Key, int> > Mapping;