Add callbacks for unresponsive render process (fixes #3661)

The client can optionally wait or terminate the render process.

Expose process exit codes via OnRenderProcessTerminated and
CefGetExitCode (fixes #2126).

cefclient: Add a new https://tests/hang page for testing hang behavior.

cefclient: Move message and resource handling to a new BaseClientHandler
class to support loading of test pages in default Chrome UI windows.

libcef_dll/ctocpp/browser_host_ctocpp.h

@@ -9,7 +9,7 @@
 // implementations. See the translator.README.txt file in the tools directory
 // for more information.
 //
-// $hash=8b1e4268c2b68437b5022e9baf3f1c56bf036fe7$
+// $hash=ec03d4b0c8e59ba8f8eb3060e374b4d76e22669b$
 //
 
 #ifndef CEF_LIBCEF_DLL_CTOCPP_BROWSER_HOST_CTOCPP_H_
@@ -139,6 +139,7 @@ class CefBrowserHostCToCpp : public CefCToCppRefCounted<CefBrowserHostCToCpp,
   bool CanExecuteChromeCommand(int command_id) override;
   void ExecuteChromeCommand(int command_id,
                             cef_window_open_disposition_t disposition) override;
+  bool IsRenderProcessUnresponsive() override;
 };
 
 #endif  // CEF_LIBCEF_DLL_CTOCPP_BROWSER_HOST_CTOCPP_H_