Move FilePathWatcher class from browser/... to common/...

chrome/browser/user_style_sheet_watcher.cc

Index: chrome/browser/user_style_sheet_watcher.cc
diff --git a/chrome/browser/user_style_sheet_watcher.cc b/chrome/browser/user_style_sheet_watcher.cc
index 347462c5e4913d21e472834fd170a0274123166c..9a314b3c4650a8a1cde716aa1c8c9cf16087b6cb 100644
--- a/chrome/browser/user_style_sheet_watcher.cc
+++ b/chrome/browser/user_style_sheet_watcher.cc
@@ -148,8 +148,12 @@ void UserStyleSheetWatcher::Init() {
     file_watcher_.reset(new FilePathWatcher);
     FilePath style_sheet_file = profile_path_.AppendASCII(kStyleSheetDir)
                                              .AppendASCII(kUserStyleSheetFile);
-    if (!file_watcher_->Watch(style_sheet_file, loader_.get()))
+    if (!file_watcher_->Watch(
+        style_sheet_file,
+        loader_.get(),
+        BrowserThread::GetMessageLoopProxyForThread(BrowserThread::UI))) {
       LOG(ERROR) << "Failed to setup watch for " << style_sheet_file.value();
+    }
     loader_->LoadStyleSheet(style_sheet_file);
   }
 }