fix webkit tests

src/api.cc

 // Copyright 2012 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 "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 80 matching lines @@
   EXCEPTION_BAILOUT_CHECK_GENERIC(                                             \
       isolate, value, isolate->FireCallCompletedCallback();)
 
 
 #define EXCEPTION_BAILOUT_CHECK(isolate, value)                                \
   EXCEPTION_BAILOUT_CHECK_GENERIC(isolate, value, ;)
 
 
 #define PREPARE_FOR_EXECUTION_GENERIC(context, function_name, bailout_value, \
                                       HandleScopeClass)                      \
-  auto isolate = reinterpret_cast<i::Isolate*>(context->GetIsolate());       \
+  auto isolate = context.IsEmpty()                                           \
+                     ? i::Isolate::Current()                                 \
+                     : reinterpret_cast<i::Isolate*>(context->GetIsolate()); \
   if (IsExecutionTerminatingCheck(isolate)) {                                \
     return bailout_value;                                                    \
   }                                                                          \
   HandleScopeClass handle_scope(isolate);                                    \
   CallDepthScope call_depth_scope(isolate, context, false);                  \
   LOG_API(isolate, function_name);                                           \
   ENTER_V8(isolate);                                                         \
   bool has_pending_exception = false
 
 
@@ skipping 7862 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal