Only measure "base" times within ProfileMode

packages/react-reconciler/src/ReactFiberScheduler.js

@@ -962,12 +962,17 @@ export default function<T, P, I, TI, HI, PI, C, CC, CX, PL>(
 
     let next;
     if (enableProfilerTimer) {
-      startBaseRenderTimer();
+      if (workInProgress.mode & ProfileMode) {
+        startBaseRenderTimer();
+      }
+
       next = beginWork(current, workInProgress, nextRenderExpirationTime);
 
-      // Update "base" time if the render wasn't bailed out on.
-      recordElapsedBaseRenderTimeIfRunning(workInProgress);
-      stopBaseRenderTimerIfRunning();
+      if (workInProgress.mode & ProfileMode) {
+        // Update "base" time if the render wasn't bailed out on.
+        recordElapsedBaseRenderTimeIfRunning(workInProgress);
+        stopBaseRenderTimerIfRunning();
+      }
     } else {
       next = beginWork(current, workInProgress, nextRenderExpirationTime);
     }

packages/react/src/__tests__/ReactProfiler-test.internal.js

@@ -108,10 +108,14 @@ describe('Profiler', () => {
   describe('onRender callback', () => {
     let AdvanceTime;
     let advanceTimeBy;
+    let mockNow;
 
     const mockNowForTests = () => {
       let currentTime = 0;
-      ReactTestRenderer.unstable_setNowImplementation(() => currentTime);
+
+      mockNow = jest.fn().mockImplementation(() => currentTime);
+
+      ReactTestRenderer.unstable_setNowImplementation(mockNow);
       advanceTimeBy = amount => {
         currentTime += amount;
       };
@@ -164,6 +168,20 @@ describe('Profiler', () => {
       expect(callback).toHaveBeenCalledTimes(1);
     });
 
+    it('does not record times for components outside of Profiler tree', () => {
+      ReactTestRenderer.create(
+        <div>
+          <AdvanceTime />
+          <AdvanceTime />
+          <AdvanceTime />
+        </div>,
+      );
+
+      // Should only be called twice, for normal expiration time purposes.
+      // No additional calls from ProfilerTimer are expected.
+      expect(mockNow).toHaveBeenCalledTimes(2);
+    });
+
     it('logs render times for both mount and update', () => {
       const callback = jest.fn();