fix: remove memory leak when using webFrame and spell checker (#16770)

* fix: do not create native api::WebFrame in webFrame

When reloading a page without restarting renderer process (for example
sandbox mode), the blink::WebFrame is not destroyed, but api::WebFrame
is always recreated for the new page context. This leaves a leak of
api::WebFrame.

* fix: remove spell checker when page context is released

spec/api-web-frame-spec.js

@@ -56,4 +56,28 @@ describe('webFrame module', function () {
     expect(words).to.deep.equal(['spleling', 'test'])
     expect(callback).to.be.true()
   })
+
+  it('top is self for top frame', () => {
+    expect(webFrame.top.context).to.equal(webFrame.context)
+  })
+
+  it('opener is null for top frame', () => {
+    expect(webFrame.opener).to.be.null()
+  })
+
+  it('firstChild is null for top frame', () => {
+    expect(webFrame.firstChild).to.be.null()
+  })
+
+  it('getFrameForSelector() does not crash when not found', () => {
+    expect(webFrame.getFrameForSelector('unexist-selector')).to.be.null()
+  })
+
+  it('findFrameByName() does not crash when not found', () => {
+    expect(webFrame.findFrameByName('unexist-name')).to.be.null()
+  })
+
+  it('findFrameByRoutingId() does not crash when not found', () => {
+    expect(webFrame.findFrameByRoutingId(-1)).to.be.null()
+  })
 })