Follow-up work from browser-engine-system migration

[pocmo]

Follow-up from #1039. This is a collection of things that are missing in the first iteration of the migration to browser-engine-system. For now I'll just collect everything here and will file separate issues as needed.

Components 0.21

• Setup tracking protection and make sure toggle behaves correctly
• Add interception implementation for firefox:home and other internal pages

Components 0.22

• (Engine does not appear to set "X-Requested-With" to "" android-components#696) "X-Requested-With" header is cleared

Components 0.23

• (Engine/Session: Fullscreen mode android-components#643) Add fullscreen API behavior
• (Extend RequestInterceptor to support error pages android-components#718) Error pages
• (browser-engine-system: Call onNavigationStateChange() earlier? android-components#728) Call onNavigationStateChange() earlier (Improvement)

Misc

• Re-add onFocusChange behavior:

  firefox-tv/app/src/amazonWebview/java/org/mozilla/focus/webview/FirefoxAmazonWebView.kt

  Lines 90 to 103 in ec097ab

  	@Suppress("UNUSED_PARAMETER") // To avoid allocation, we use a function reference but it's on a platform interface.
  	private fun onFocusChange(view: View, hasFocus: Boolean): Unit = if (!hasFocus) {
  	// For why we're modifying the focusedDOMElement, see FocusedDOMElementCache.
  	//
  	// Any views (like BrowserNavigationOverlay) that may clear the cache, e.g. by
  	// reloading the page, are required to handle their own caching. Here we'll handle
  	// cases where the page cache isn't cleared.
  	focusedDOMElement.cache()
  	} else {
  	// Trying to restore immediately doesn't work - perhaps the WebView hasn't actually
  	// received focus yet? Posting to the end of the UI queue seems to solve the problem.
  	uiHandler.post { focusedDOMElement.restore() }
  	Unit
  	}

  
  To test this is fixed:

To test this is fixed:
Open YT.com/tv
Open menu
Close menu
move selection
expected: selection moves
actual: user cannot move selection

• InfoFragment: Do we need to hide the WebView if we are loading an internal page?
• InfoFragment: Do we need to re-add to onPageStart(): progressView.announceForAccessibility(getString(R.string.accessibility_announcement_loading));
• The back/forward state in the toolbar updates very slowly. It looks like you need to move the cursor around to make it refresh at times (?!). (Improved this and filed an a-c issue to improve this).
• Internal pages are now black text on a white background?

QA

• Make sure EngineView.scrollByClamped performs fast. Consider adding API to EngineView.
• Make sure tracking protection is disabled in InfoFragment (Is that strictly required?)
• Make sure back/forward navigation is working properly. Fixed it to behave consistently - but actual behavior is to be defined in # [1304] Define navigation flow involving history and the overlay #1071.
• Make sure handling external URLs (with fallback) are working properly (Do we even support that?)

Crashes

• STR (Nexus 9): Launch, Click Rotten Tomatoes tile, wait for page to load, press back.

 E  java.lang.IllegalStateException: No selected session
 E      at mozilla.components.browser.session.SessionManager.getSelectedSessionOrThrow(SessionManager.kt:56)
 E      at mozilla.components.feature.session.SessionUseCases$LoadUrlUseCase.invoke$default(SessionUseCases.kt:27)
 E      at org.mozilla.focus.browser.BrowserFragment.loadUrl(BrowserFragment.kt:280)
 E      at org.mozilla.focus.ScreenController.showBrowserScreenForUrl(ScreenController.kt:92)
 E      at org.mozilla.focus.MainActivity$sessionObserver$1.onNoActiveSession(MainActivity.kt:65)
 E      at org.mozilla.focus.MainActivity$sessionObserver$1.onSessionRemoved(MainActivity.kt:55)
 E      at mozilla.components.browser.session.SessionManager$remove$$inlined$synchronized$lambda$1.invoke(SessionManager.kt:158)
 E      at mozilla.components.browser.session.SessionManager$remove$$inlined$synchronized$lambda$1.invoke(SessionManager.kt:16)
 E      at mozilla.components.support.base.observer.ObserverRegistry.notifyObservers(ObserverRegistry.kt:106)
 E      at mozilla.components.browser.session.SessionManager.notifyObservers(SessionManager.kt)
 E      at mozilla.components.browser.session.SessionManager.remove(SessionManager.kt:158)
 E      at mozilla.components.browser.session.SessionManager.remove$default(SessionManager.kt:127)
 E      at org.mozilla.focus.browser.BrowserFragment.onBackPressed(BrowserFragment.kt:270)
 E      at org.mozilla.focus.MainActivity.onBackPressed(MainActivity.kt:154)
 E      at android.app.Activity.onKeyUp(Activity.java:2725)

[pocmo]

Created to follow-ups: #1077, #1076.

[mcomella]

It looks like most of these items are addressed.

[mcomella]

And we haven't been seeing any urgent problems: closing.