linux_aura: Don't clear target vector in SelectionOwner.

This was causing an intermittent crash in the SelectionClear unit
tests, since it cleared the TARGETS atom out of the list of offered
types

BUG=none

Review URL: https://codereview.chromium.org/129763002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243985 0039d316-1c4b-4281-b951-d872f2087c98

ui/base/x/selection_owner.cc

@@ -39,7 +39,6 @@ SelectionOwner::~SelectionOwner() {
 }
 
 void SelectionOwner::RetrieveTargets(std::vector<Atom>* targets) {
-  targets->clear();
   for (SelectionFormatMap::const_iterator it = format_map_.begin();
        it != format_map_.end(); ++it) {
     targets->push_back(it->first);

ui/base/x/selection_owner.h

@@ -35,7 +35,7 @@ class UI_BASE_EXPORT SelectionOwner {
   // Returns the current selection data. Useful for fast paths.
   const SelectionFormatMap& selection_format_map() { return format_map_; }
 
-  // Retrieves a list of types we're offering.
+  // Appends a list of types we're offering to |targets|.
   void RetrieveTargets(std::vector<Atom>* targets);
 
   // Attempts to take ownership of the selection. If we're successful, present