Fix an issue with not clearing |selected_text_| when text selection range is empty (Mac)

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index d7c05d394688908451d1dc31bd77d54eb49d3238..4f9fa204a0a5f8620f68621df1c634d809d0259b 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1011,8 +1011,9 @@ void RenderWidgetHostViewMac::OnTextSelectionChanged(
       GetTextInputManager()->GetTextSelection(focused_view);
 
   base::string16 text;
-  if (selection->GetSelectedText(&text))
-    selected_text_ = base::UTF16ToUTF8(text);
+  if (!selection->GetSelectedText(&text))
+    return;
+  selected_text_ = base::UTF16ToUTF8(text);
 
   [cocoa_view_ setSelectedRange:selection->range.ToNSRange()];
   // Updates markedRange when there is no marked text so that retrieving