Closes #847: Implement onCancelEditing to handle keyboard backPress (#929)

app/src/main/java/org/mozilla/fenix/components/toolbar/ToolbarComponent.kt

@@ -67,6 +67,7 @@ sealed class SearchAction : Action {
     data class TextChanged(val query: String) : SearchAction()
     object ToolbarTapped : SearchAction()
     data class ToolbarMenuItemTapped(val item: ToolbarMenu.Item) : SearchAction()
+    object EditingCanceled : SearchAction()
 }
 
 sealed class SearchChange : Change {

app/src/main/java/org/mozilla/fenix/components/toolbar/ToolbarUIView.kt

@@ -55,7 +55,8 @@ class ToolbarUIView(
 
             setOnEditListener(object : mozilla.components.concept.toolbar.Toolbar.OnEditListener {
                 override fun onCancelEditing(): Boolean {
-                    return true
+                    actionEmitter.onNext(SearchAction.EditingCanceled)
+                    return false
                 }
                 override fun onTextChanged(text: String) {
                     url = text

app/src/main/java/org/mozilla/fenix/search/SearchFragment.kt

@@ -79,6 +79,7 @@ class SearchFragment : Fragment() {
 
     override fun onStart() {
         super.onStart()
+
         getAutoDisposeObservable<SearchAction>()
             .subscribe {
                 when (it) {
@@ -91,6 +92,9 @@ class SearchFragment : Fragment() {
                     is SearchAction.TextChanged -> {
                         getManagedEmitter<AwesomeBarChange>().onNext(AwesomeBarChange.UpdateQuery(it.query))
                     }
+                    is SearchAction.EditingCanceled -> {
+                        activity?.onBackPressed()
+                    }
                 }
             }