Fall back to using browser instead of document to get current URL.

To maintain compatibility with other WebDriver implementations, the
IE driver uses the IHTMLDocument2 interface to get the current URL,
so that the proper URL is returned even when an embedded frame has
the focus. However, when browsing a non-HTML document (like a PDF),
the driver cannot get an IHTMLDocument2. In that case, fall back to
the IWebBrowser2 interface.

cpp/iedriver/CommandHandlers/GetCurrentUrlCommandHandler.h

@@ -43,20 +43,25 @@ class GetCurrentUrlCommandHandler : public IECommandHandler {
       return;
     }
 
+    std::string current_url = "";
     CComPtr<IHTMLDocument2> top_level_document;
     browser_wrapper->GetDocument(true, &top_level_document);
     if (!top_level_document) {
-      LOG(WARN) << "Unable to get document from browser. Are you viewing a non-HTML document?";
+      LOG(WARN) << "Unable to get document from browser. Are you viewing a "
+                << "non-HTML document? Falling back to potentially "
+                << "inconsistent method for obtaining URL.";
+      current_url = browser_wrapper->GetBrowserUrl();
+    } else {
+      CComBSTR url;
+      HRESULT hr = top_level_document->get_URL(&url);
+      if (FAILED(hr)) {
+        LOGHR(WARN, hr) << "IHTMLDocument2::get_URL failed.";
+      }
+
+      std::wstring converted_url(url, ::SysStringLen(url));
+      current_url = StringUtilities::ToString(converted_url);
     }
 
-    CComBSTR url;
-    HRESULT hr = top_level_document->get_URL(&url);
-    if (FAILED(hr)) {
-      LOGHR(WARN, hr) << "IHTMLDocument2::get_URL failed.";
-    }
-
-    std::wstring converted_url(url, ::SysStringLen(url));
-    std::string current_url = StringUtilities::ToString(converted_url);
     response->SetSuccessResponse(current_url);
   }
 };