Test (and fix) all exception paths that can occur with proxies.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index c941f536192ea8690cb7999ace08cb3ec6c4166f..bf28e0ad6859890b49bd082751f63bc1fc2cdc36 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -238,6 +238,7 @@ MaybeObject* Object::GetPropertyWithHandler(Object* receiver_raw,
   // Extract trap function.
   Handle<String> trap_name = isolate->factory()->LookupAsciiSymbol("get");
   Handle<Object> trap(v8::internal::GetProperty(handler, trap_name));
+  if (isolate->has_pending_exception()) return Failure::Exception();
   if (trap->IsUndefined()) {
     // Get the derived `get' property.
     trap = isolate->derived_get_trap();
@@ -2255,6 +2256,7 @@ bool JSProxy::HasPropertyWithHandler(String* name_raw) {
   // Extract trap function.
   Handle<String> trap_name = isolate->factory()->LookupAsciiSymbol("has");
   Handle<Object> trap(v8::internal::GetProperty(handler, trap_name));
+  if (isolate->has_pending_exception()) return Failure::Exception();
   if (trap->IsUndefined()) {
     trap = isolate->derived_has_trap();
   }
@@ -2285,6 +2287,7 @@ MUST_USE_RESULT MaybeObject* JSProxy::SetPropertyWithHandler(
   // Extract trap function.
   Handle<String> trap_name = isolate->factory()->LookupAsciiSymbol("set");
   Handle<Object> trap(v8::internal::GetProperty(handler, trap_name));
+  if (isolate->has_pending_exception()) return Failure::Exception();
   if (trap->IsUndefined()) {
     trap = isolate->derived_set_trap();
   }
@@ -2312,6 +2315,7 @@ MUST_USE_RESULT MaybeObject* JSProxy::DeletePropertyWithHandler(
   // Extract trap function.
   Handle<String> trap_name = isolate->factory()->LookupAsciiSymbol("delete");
   Handle<Object> trap(v8::internal::GetProperty(handler, trap_name));
+  if (isolate->has_pending_exception()) return Failure::Exception();
   if (trap->IsUndefined()) {
     Handle<Object> args[] = { handler, trap_name };
     Handle<Object> error = isolate->factory()->NewTypeError(
@@ -2353,6 +2357,7 @@ MUST_USE_RESULT PropertyAttributes JSProxy::GetPropertyAttributeWithHandler(
   Handle<String> trap_name =
       isolate->factory()->LookupAsciiSymbol("getPropertyDescriptor");
   Handle<Object> trap(v8::internal::GetProperty(handler, trap_name));
+  if (isolate->has_pending_exception()) return NONE;
   if (trap->IsUndefined()) {
     Handle<Object> args[] = { handler, trap_name };
     Handle<Object> error = isolate->factory()->NewTypeError(