Clear pending message during Isolate::CancelScheduledExceptionFromTryCatch.

test/unittests/api/exception-unittest.cc

Index: test/unittests/api/exception-unittest.cc
diff --git a/test/unittests/api/exception-unittest.cc b/test/unittests/api/exception-unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b8f21cc4e294cc3099e64584e3d36aa4def1f77a
--- /dev/null
+++ b/test/unittests/api/exception-unittest.cc
@@ -0,0 +1,45 @@
+// Copyright 2017 the V8 project 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 "include/v8.h"
+#include "src/flags.h"
+#include "test/unittests/test-utils.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace v8 {
+namespace {
+
+using APIExceptionTest = TestWithIsolate;
+
+class ScopedExposeGc {
+ public:
+  ScopedExposeGc() : was_exposed_(i::FLAG_expose_gc) {
+    i::FLAG_expose_gc = true;
+  }
+  ~ScopedExposeGc() { i::FLAG_expose_gc = was_exposed_; }
+
+ private:
+  const bool was_exposed_;
+};
+
+TEST_F(APIExceptionTest, ExceptionMessageDoesNotKeepContextAlive) {
+  ScopedExposeGc expose_gc;
+  Persistent<Context> weak_context;
+  {
+    HandleScope handle_scope(isolate());
+    Local<Context> context = Context::New(isolate());
+    weak_context.Reset(isolate(), context);
+    weak_context.SetWeak();
+
+    Context::Scope context_scope(context);
+    TryCatch try_catch(isolate());
+    isolate()->ThrowException(Undefined(isolate()));
+  }
+  isolate()->RequestGarbageCollectionForTesting(
+      Isolate::kFullGarbageCollection);
+  EXPECT_TRUE(weak_context.IsEmpty());
+}
+
+}  // namespace
+}  // namespace v8