fixes for useIsolation

lighthouse-core/gather/driver.js

@@ -86,6 +86,14 @@ class Driver {
       this._handleReceivedMessageFromTarget(event, []).catch(this._handleEventError);
     });
 
+    this.on('Runtime.executionContextDestroyed', event => {
+      if (event.executionContextId === this._isolatedExecutionContextId) {
+        this._clearIsolatedContextId();
+      }
+    });
+
+    this.on('Page.frameNavigated', this._clearIsolatedContextId.bind(this));
+
     connection.on('protocolevent', this._handleProtocolEvent.bind(this));
 
     /**
@@ -464,7 +472,16 @@ class Driver {
    */
   async evaluateAsync(expression, options = {}) {
     const contextId = options.useIsolation ? await this._getOrCreateIsolatedContextId() : undefined;
-    return this._evaluateInContext(expression, contextId);
+    return this._evaluateInContext(expression, contextId).catch(async err => {
+      // If we were using isolation and the context disappeared on us, retry one more time.
+      if (contextId && err.message.includes('Cannot find context')) {
+        this._clearIsolatedContextId();
+        const freshContextId = await this._getOrCreateIsolatedContextId();
+        return this._evaluateInContext(expression, freshContextId);
+      }
+
+      throw err;
+    });
   }
 
   /**

lighthouse-core/test/gather/driver-test.js

@@ -317,6 +317,19 @@ describe('.evaluateAsync', () => {
       expect.anything()
     );
   });
+
+  it('recovers from isolation failures', async () => {
+    connectionStub.sendCommand = createMockSendCommandFn()
+      .mockResponse('Page.getResourceTree', {frameTree: {frame: {id: 1337}}})
+      .mockResponse('Page.createIsolatedWorld', {executionContextId: 9001})
+      .mockResponse('Runtime.evaluate', Promise.reject(new Error('Cannot find context')))
+      .mockResponse('Page.getResourceTree', {frameTree: {frame: {id: 1337}}})
+      .mockResponse('Page.createIsolatedWorld', {executionContextId: 9002})
+      .mockResponse('Runtime.evaluate', {result: {value: 2}});
+
+    const value = await driver.evaluateAsync('1 + 1', {useIsolation: true});
+    expect(value).toEqual(2);
+  });
 });
 
 describe('.sendCommand', () => {

lighthouse-core/test/gather/gather-runner-test.js

@@ -579,7 +579,7 @@ describe('GatherRunner', function() {
       afterPass(context) {
         context.driver.scrollTo({x: 1000, y: 1000});
       }
-    };
+    }
 
     const url = 'https://example.com';
     const driver = Object.assign({}, fakeDriver);