Remove implicit conversions from scoped_refptr to T* in base/

This patch was generated by running the rewrite_scoped_refptr clang tool
on a Mac build.

BUG=110610

Review URL: https://codereview.chromium.org/584883003

Cr-Commit-Position: refs/heads/master@{#295855}

base/files/file_path_watcher_mac.cc

@@ -34,13 +34,13 @@ class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate {
   }
 
   virtual void Cancel() OVERRIDE {
-    if (impl_)
+    if (impl_.get())
       impl_->Cancel();
     set_cancelled();
   }
 
   virtual void CancelOnMessageLoopThread() OVERRIDE {
-    if (impl_)
+    if (impl_.get())
       impl_->Cancel();
     set_cancelled();
   }