Fix DevTools bug with Suspense+LegacyHidden component (facebook#21432)

Author: Brian Vaughn

packages/react-devtools-shared/src/backend/agent.js

@@ -676,7 +676,10 @@ export default class Agent extends EventEmitter<{|
 
   onHookOperations = (operations: Array<number>) => {
     if (__DEBUG__) {
-      debug('onHookOperations', operations);
+      debug(
+        'onHookOperations',
+        `(${operations.length}) [${operations.join(', ')}]`,
+      );
     }
 
     // TODO:

packages/react-devtools-shared/src/backend/renderer.js

@@ -534,6 +534,7 @@ export function attach(
     HostText,
     IncompleteClassComponent,
     IndeterminateComponent,
+    LegacyHiddenComponent,
     MemoComponent,
     OffscreenComponent,
     SimpleMemoComponent,
@@ -841,6 +842,7 @@ export function attach(
       case HostPortal:
       case HostText:
       case Fragment:
+      case LegacyHiddenComponent:
       case OffscreenComponent:
         return true;
       case HostRoot: