If the user selects text in the current tab, and types CTRL-F,...

chrome/browser/renderer_host/render_view_host.cc

Index: chrome/browser/renderer_host/render_view_host.cc
===================================================================
--- chrome/browser/renderer_host/render_view_host.cc	(revision 71618)
+++ chrome/browser/renderer_host/render_view_host.cc	(working copy)
@@ -1313,6 +1313,7 @@
 }
 
 void RenderViewHost::OnMsgSelectionChanged(const std::string& text) {
+  selected_text_ = text;
   if (view())
     view()->SelectionChanged(text);
 }
@@ -1820,6 +1821,10 @@
   }
 }
 
+std::string RenderViewHost::selected_text() {
+  return selected_text_;
+}
+
 void RenderViewHost::JavaScriptStressTestControl(int cmd, int param) {
   Send(new ViewMsg_JavaScriptStressTestControl(routing_id(), cmd, param));
 }