Protect against API abuse.

This makes Chrome's --single-process work again, but the real solution
is to pass an Isolate explicitly and fixing things on the Chrome side
=> follow-up CLs.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/239513006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/api.cc

@@ -6291,12 +6291,16 @@ void V8::SetCaptureStackTraceForUncaughtExceptions(
 
 void V8::SetCounterFunction(CounterLookupCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->SetCounterFunction(callback);
 }
 
 
 void V8::SetCreateHistogramFunction(CreateHistogramCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->SetCreateHistogramFunction(callback);
   isolate->InitializeLoggingAndCounters();
   isolate->counters()->ResetHistograms();
@@ -6305,6 +6309,8 @@ void V8::SetCreateHistogramFunction(CreateHistogramCallback callback) {
 
 void V8::SetAddHistogramSampleFunction(AddHistogramSampleCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->
       SetAddHistogramSampleFunction(callback);
 }