[inspector] exposed ExecutionContextId getter by context

BUG=none
R=pfeldman@chromium.org

Review-Url: https://codereview.chromium.org/2690663003
Cr-Commit-Position: refs/heads/master@{#43122}

include/v8-inspector.h

@@ -85,6 +85,8 @@ class V8_EXPORT V8ContextInfo {
   StringView auxData;
   bool hasMemoryOnConsole;
 
+  static int executionContextId(v8::Local<v8::Context> context);
+
  private:
   // Disallow copying and allocating this one.
   enum NotNullTagEnum { NotNullLiteral };

src/inspector/v8-inspector-session-impl.cc

@@ -37,6 +37,11 @@ bool V8InspectorSession::canDispatchMethod(const StringView& method) {
                               protocol::Schema::Metainfo::commandPrefix);
 }
 
+// static
+int V8ContextInfo::executionContextId(v8::Local<v8::Context> context) {
+  return InspectedContext::contextId(context);
+}
+
 std::unique_ptr<V8InspectorSessionImpl> V8InspectorSessionImpl::create(
     V8InspectorImpl* inspector, int contextGroupId,
     V8Inspector::Channel* channel, const StringView& state) {