[chromedriver] Support clicking an element in sub frames.

chrome/test/chromedriver/session.cc

Index: chrome/test/chromedriver/session.cc
diff --git a/chrome/test/chromedriver/session.cc b/chrome/test/chromedriver/session.cc
index d65a42729d12c34201898914650d0798bfca0096..eaeda0944cfdffaa06a3b648b309d64e8179fc05 100644
--- a/chrome/test/chromedriver/session.cc
+++ b/chrome/test/chromedriver/session.cc
@@ -52,6 +52,17 @@ Status Session::GetTargetWindow(WebView** web_view) {
   return Status(kNoSuchWindow, "target window already closed");
 }
 
+void Session::SetToFrame(const std::string& new_frame,
+                         const std::string& xpath) {
+  if (new_frame.empty()) {
+    frame = "";
+    frame_elements.clear();
+  } else {
+    frame_elements.push_back(FrameInfo(frame, xpath));
+    frame = new_frame;
+  }
+}
+
 scoped_ptr<base::DictionaryValue> Session::CreateCapabilities() {
   scoped_ptr<base::DictionaryValue> caps(new base::DictionaryValue());
   caps->SetString("browserName", "chrome");