<webview>: Add support for filtering extension events by instanceId.

extensions/common/event_matcher.cc

Index: extensions/common/event_matcher.cc
diff --git a/extensions/common/event_matcher.cc b/extensions/common/event_matcher.cc
index c9829373c9102a16a331066f346c19fb0e8d2eef..937c783745f5182d7bd539178afd220570fef496 100644
--- a/extensions/common/event_matcher.cc
+++ b/extensions/common/event_matcher.cc
@@ -21,8 +21,9 @@ EventMatcher::~EventMatcher() {
 
 bool EventMatcher::MatchNonURLCriteria(
     const EventFilteringInfo& event_info) const {
-  // There is currently no criteria apart from URL criteria.
-  return true;
+  if (!event_info.has_instance_id())
+    return true;
+  return event_info.instance_id() == GetInstanceID();
 }
 
 int EventMatcher::GetURLFilterCount() const {
@@ -44,4 +45,10 @@ int EventMatcher::HasURLFilters() const {
   return GetURLFilterCount() != 0;
 }
 
+int EventMatcher::GetInstanceID() const {
+  int instance_id = 0;
+  filter_->GetInteger("instanceId", &instance_id);
+  return instance_id;
+}
+
 }  // namespace extensions