Fix issue when firing TimerProc() destroys timer

fpdfsdk/fpdfformfill_embeddertest.cpp

 // Copyright 2015 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "public/fpdf_formfill.h"
 #include "testing/embedder_test.h"
 #include "testing/embedder_test_mock_delegate.h"
 #include "testing/embedder_test_timer_handling_delegate.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 115 matching lines @@
   FPDF_PAGE page = LoadPage(0);
   EXPECT_TRUE(page);
   DoOpenActions();
   delegate.AdvanceTime(5000);
   UnloadPage(page);
 
   const auto& alerts = delegate.GetAlerts();
   EXPECT_EQ(0U, alerts.size());
 }
 
+TEST_F(FPDFFormFillEmbeddertest, BUG_634394) {
+  // Cancel timer inside timer callback.
+  EmbedderTestTimerHandlingDelegate delegate;
+  SetDelegate(&delegate);
+
+  EXPECT_TRUE(OpenDocument("bug_634394.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  EXPECT_TRUE(page);
+  DoOpenActions();
+
+  // Timers fire at most once per AdvanceTime(), allow intervals
+  // to fire several times if possible.
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  delegate.AdvanceTime(1000);
+  UnloadPage(page);
+
+  const auto& alerts = delegate.GetAlerts();
+  EXPECT_EQ(2U, alerts.size());
+}
+
 #endif  // PDF_ENABLE_V8