### Describe what you were doing when the bug occurred:
1. I did profiling on a list, that gets updated on each pagination api call.
2. Once the profiling was done, I moved around in the Profiler to view the Flamegraph
3. Moving to second capture, the Profiler crashed.


**DevTools version**: 4.6.0-6cceaeb67

```
Component stack: in ec
    in div
    in div
    in div
    in So
    in Unknown
    in n
    in Unknown
    in div
    in div
    in rl
    in Ze
    in fn
    in Ga
    in _s
```
case PROFILER_NUMBER:
          case PROFILER_SYMBOL_STRING:
            return ElementTypeProfiler;
          default:
            return ElementTypeOtherOrUnknown;
        }
    }
  }
   This is a slightly annoying indirection.
   It is currently necessary because DevTools wants to use unique objects as keys for instances.
   However fibers have two versions.
   We use this set to remember first encountered fiber for each conceptual instance.
  function getPrimaryFiber(fiber: Fiber): Fiber {
    if (primaryFibers.has(fiber)) {
      return fiber;
    }
    const {alternate} = fiber;
    if (alternate != null && primaryFibers.has(alternate)) {
      return alternate;
    }
    primaryFibers.add(fiber);
    return fiber;
  }
  const fiberToIDMap: Map<Fiber, number> = new Map();
  const idToFiberMap: Map<number, Fiber> = new Map();
  const primaryFibers: Set<Fiber> = new Set();
   When profiling is supported, we store the latest tree base durations for each Fiber.
   This is so that we can quickly capture a snapshot of those values if profiling starts.
   If we didn't store these values, we'd have to crawl the tree when profiling started,
   and use a slow path to find each of the current Fibers.