Assert that context creation doesn't throw

src/execution.h

Index: src/execution.h
diff --git a/src/execution.h b/src/execution.h
index f26ea343082b93f68d1ac088971bef15880adc7b..ee5d3a6f738f2e8336c13ca18b0f4ba5565cc287 100644
--- a/src/execution.h
+++ b/src/execution.h
@@ -15,6 +15,9 @@ namespace internal {
 
 class Execution final : public AllStatic {
  public:
+  // Whether to report pending messages, or keep them pending on the isolate.
+  enum class MessageHandling { kReport, kKeepPending };
+
   // Call a function, the caller supplies a receiver and an array
   // of arguments.
   //
@@ -36,16 +39,18 @@ class Execution final : public AllStatic {
                                                  int argc,
                                                  Handle<Object> argv[]);
 
-  // Call a function, just like Call(), but make sure to silently catch
-  // any thrown exceptions. The return value is either the result of
-  // calling the function (if caught exception is false) or the exception
-  // that occurred (if caught exception is true).
-  // In the exception case, exception_out holds the caught exceptions, unless
-  // it is a termination exception.
+  // Call a function, just like Call(), but handle don't report exceptions
+  // externally.
+  // The return value is either the result of calling the function (if no
+  // exception occurred), or an empty handle.
+  // If message_handling is MessageHandling::kReport, exceptions (except for
+  // termination exceptions) will be stored in exception_out (if not a
+  // nullptr).
   static MaybeHandle<Object> TryCall(Isolate* isolate, Handle<Object> callable,
                                      Handle<Object> receiver, int argc,
                                      Handle<Object> argv[],
-                                     MaybeHandle<Object>* exception_out = NULL);
+                                     MessageHandling message_handling,
+                                     MaybeHandle<Object>* exception_out);
 };