Try to reduce the flankness of the PPAPI UI tests.

ppapi/tests/testing_instance.h

Index: ppapi/tests/testing_instance.h
===================================================================
--- ppapi/tests/testing_instance.h	(revision 98050)
+++ ppapi/tests/testing_instance.h	(working copy)
@@ -17,6 +17,23 @@
 
 class TestCase;
 
+// How signaling works:
+//
+// We want to signal to the Chrome UI test harness
+// (chrome/test/ui/ppapi_uitest.cc) that we're making progress and when we're
+// done. The easiest thing in the UI test infrastructure is to wait for a
+// cookie to become nonempty. We don't want to have a big wait for all tests in
+// a TestCase since they can take a while and it might timeout.  So we set a
+// series of cookies with an incrementing number in the name.
+//
+// If the value of the cookie is "..." then that tells the test runner that
+// the test is progressing. It then waits for the next numbered cookie until
+// it either times out or the value is something other than "...". In this
+// case, the value will be either "PASS" or "FAIL [optional message]"
+// corresponding to the outcome of the entire test case. Timeout will be
+// treated just like a failure of the entire test case and the test will be
+// terminated.
+//
 // In trusted builds, we use InstancePrivate and allow tests that use
 // synchronous scripting. NaCl does not support synchronous scripting.
 class TestingInstance : public
@@ -81,6 +98,8 @@
   // Appends the given HTML string to the console in the document.
   void LogHTML(const std::string& html);
 
+  void ReportProgress(const std::string& progress_value);
+
   // Sets the given cookie in the current document.
   void SetCookie(const std::string& name, const std::string& value);
 
@@ -89,6 +108,10 @@
   // Owning pointer to the current test case. Valid after Init has been called.
   TestCase* current_case_;
 
+  // The current step we're on starting at 0. This is incremented every time we
+  // report progress via a cookie. See comment above the class.
+  int progress_cookie_number_;
+
   // Set once the tests are run so we know not to re-run when the view is sized.
   bool executed_tests_;