bookmarks: Move BaseBookmarkModelObserver into 'bookmarks' namespace.

components/bookmarks/browser/base_bookmark_model_observer.h

Index: components/bookmarks/browser/base_bookmark_model_observer.h
diff --git a/components/bookmarks/browser/base_bookmark_model_observer.h b/components/bookmarks/browser/base_bookmark_model_observer.h
index ae1c6b925ead3162cfde894e30a7d8aa9a64e3e5..37a010787e0f1bb907c6bdc94576f3550c2f11ab 100644
--- a/components/bookmarks/browser/base_bookmark_model_observer.h
+++ b/components/bookmarks/browser/base_bookmark_model_observer.h
@@ -9,6 +9,8 @@
 #include "base/compiler_specific.h"
 #include "components/bookmarks/browser/bookmark_model_observer.h"
 
+namespace bookmarks {
+
 // Base class for a BookmarkModelObserver implementation. All mutations of the
 // model funnel into the method BookmarkModelChanged.
 class BaseBookmarkModelObserver : public BookmarkModelObserver {
@@ -49,4 +51,6 @@ class BaseBookmarkModelObserver : public BookmarkModelObserver {
   DISALLOW_COPY_AND_ASSIGN(BaseBookmarkModelObserver);
 };
 
+}  // namespace bookmarks
+
 #endif  // COMPONENTS_BOOKMARKS_BROWSER_BASE_BOOKMARK_MODEL_OBSERVER_H_