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• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• All existing tests are passing: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/DevelopmentWorkflow.md#running-unit-tests-application.
• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

What is the current behavior?

The commit ab5fa94 seems to have broken the resume of the app in some situations, e.g. when switching back from nativescript-inappbrowser. As illustrated by this repo.

On closing the browser you get a crash on android with the stack:

  TNS.Native: setRootViewCSSClasses(file: app/webpack:/testpopcrash/node_modules/@nativescript/core/application/application-common.js:151:0)
  TNS.Native:   at initRootView(file: app/webpack:/testpopcrash/node_modules/@nativescript/core/application/application-common.js:221:0)
  TNS.Native:   at setActivityContent(file: app/webpack:/testpopcrash/node_modules/@nativescript/core/ui/frame/index.android.js:1190:19)
  TNS.Native:   at onCreate(file: app/webpack:/testpopcrash/node_modules/@nativescript/core/ui/frame/index.android.js:1003:0)
  TNS.Native:   at onCreate(file: app/webpack:/testpopcrash/node_modules/@nativescript/core/ui/frame/activity.android.js:21:0)

The reason is that the application.foregroundActivity is undefined, and the startActivity is a chromeManagerActivity, and the code then fails to resolve the rootView.

What is the new behavior?

This change modifies initRootView to accept a root view, since all calling code seems to already have the rootView and can pass it in.