Assert that context creation doesn't throw

src/execution.h

 // Copyright 2014 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.
 
 #ifndef V8_EXECUTION_H_
 #define V8_EXECUTION_H_
 
 #include "src/allocation.h"
 #include "src/base/atomicops.h"
 #include "src/handles.h"
@@ skipping 18 matching lines @@
   // arguments.
   MUST_USE_RESULT static MaybeHandle<Object> New(Handle<JSFunction> constructor,
                                                  int argc,
                                                  Handle<Object> argv[]);
   MUST_USE_RESULT static MaybeHandle<Object> New(Isolate* isolate,
                                                  Handle<Object> constructor,
                                                  Handle<Object> new_target,
                                                  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 an exception was raised and exception_out is non-nullptr,  holds the
+  // caught exceptions, unless it is a termination exception. Otherwise, the
+  // exception is kept pending on the isolate.

[Yang, 2017/01/17 09:54:23]

Wait... if exception_out is nullptr, TryCall behaves the same as Call?

[jochen (gone - plz use gerrit), 2017/01/17 10:24:01]

no, Call() schedules the exception, TryCall leaves it pending

tried to clarify the comment

   static MaybeHandle<Object> TryCall(Isolate* isolate, Handle<Object> callable,
                                      Handle<Object> receiver, int argc,
                                      Handle<Object> argv[],
-                                     MaybeHandle<Object>* exception_out = NULL);
+                                     MaybeHandle<Object>* exception_out);
 };
 
 
 class ExecutionAccess;
 class PostponeInterruptsScope;
 
 
 // StackGuard contains the handling of the limits that are used to limit the
 // number of nested invocations of JavaScript and the stack size used in each
 // invocation.
@@ skipping 159 matching lines @@
   friend class StackLimitCheck;
   friend class PostponeInterruptsScope;
 
   DISALLOW_COPY_AND_ASSIGN(StackGuard);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_EXECUTION_H_