Fix: Don't apply single-origin mode to native apps (#667)

An unwarranted use of the Elivs operator in Form.kt makes it such that
the restrictions of single-origin mode also apply to native apps.

This commit fixes the bug and also reduces the number of intermediate
values that can mask mistakes like this one.

It also renames saveFlag to saveFlags in BrowserAutofillSupportInfo
since this variable is not limited to contain only a single flag.

app/src/main/java/com/zeapo/pwdstore/autofill/oreo/FeatureAndTrustDetection.kt

@@ -141,7 +141,7 @@ private fun getBrowserSaveFlag(appPackage: String): Int? = BROWSER_SAVE_FLAG[app
 
 data class BrowserAutofillSupportInfo(
     val multiOriginMethod: BrowserMultiOriginMethod,
-    val saveFlag: Int?
+    val saveFlags: Int?
 )
 
 @RequiresApi(Build.VERSION_CODES.O)
@@ -152,7 +152,7 @@ fun getBrowserAutofillSupportInfoIfTrusted(
     if (!isTrustedBrowser(context, appPackage)) return null
     return BrowserAutofillSupportInfo(
         multiOriginMethod = getBrowserMultiOriginMethod(appPackage),
-        saveFlag = getBrowserSaveFlag(appPackage)
+        saveFlags = getBrowserSaveFlag(appPackage)
     )
 }
 
@@ -175,7 +175,7 @@ private fun getBrowserAutofillSupportLevel(
     val browserInfo = getBrowserAutofillSupportInfoIfTrusted(context, appPackage)
     return when {
         browserInfo == null -> BrowserAutofillSupportLevel.None
-        browserInfo.saveFlag != null -> BrowserAutofillSupportLevel.FillAndSave
+        browserInfo.saveFlags != null -> BrowserAutofillSupportLevel.FillAndSave
         appPackage in FLAKY_BROWSERS -> BrowserAutofillSupportLevel.FlakyFill
         else -> BrowserAutofillSupportLevel.Fill
     }

app/src/main/java/com/zeapo/pwdstore/autofill/oreo/Form.kt

@@ -81,15 +81,9 @@ private class Form(context: Context, structure: AssistStructure, isManualRequest
 
     private var appPackage = structure.activityComponent.packageName
 
-    private val browserAutofillSupportInfo =
+    private val trustedBrowserInfo =
         getBrowserAutofillSupportInfoIfTrusted(context, appPackage)
-    private val isTrustedBrowser = browserAutofillSupportInfo != null
+    val saveFlags = trustedBrowserInfo?.saveFlags
-
-    private val browserMultiOriginMethod =
-        browserAutofillSupportInfo?.multiOriginMethod ?: BrowserMultiOriginMethod.None
-    private val singleOriginMode = browserMultiOriginMethod == BrowserMultiOriginMethod.None
-
-    val saveFlags = browserAutofillSupportInfo?.saveFlag
 
     private val webOrigins = mutableSetOf<String>()
 
@@ -114,7 +108,7 @@ private class Form(context: Context, structure: AssistStructure, isManualRequest
     private fun visitFormNode(node: AssistStructure.ViewNode, inheritedWebOrigin: String? = null) {
         trackOrigin(node)
         val field =
-            if (browserMultiOriginMethod == BrowserMultiOriginMethod.WebView) {
+            if (trustedBrowserInfo?.multiOriginMethod == BrowserMultiOriginMethod.WebView) {
                 FormField(node, fieldIndex, true, inheritedWebOrigin)
             } else {
                 check(inheritedWebOrigin == null)
@@ -135,12 +129,12 @@ private class Form(context: Context, structure: AssistStructure, isManualRequest
 
     private fun detectFieldsToFill(isManualRequest: Boolean) = autofillStrategy.match(
         relevantFields,
-        singleOriginMode = singleOriginMode,
+        singleOriginMode = trustedBrowserInfo?.multiOriginMethod == BrowserMultiOriginMethod.None,
         isManualRequest = isManualRequest
     )
 
     private fun trackOrigin(node: AssistStructure.ViewNode) {
-        if (!isTrustedBrowser) return
+        if (trustedBrowserInfo == null) return
         node.webOrigin?.let {
             if (it !in webOrigins) {
                 d { "Origin encountered: $it" }
@@ -159,14 +153,14 @@ private class Form(context: Context, structure: AssistStructure, isManualRequest
 
     private fun determineFormOrigin(context: Context): FormOrigin? {
         if (scenario == null) return null
-        if (!isTrustedBrowser || webOrigins.isEmpty()) {
+        if (trustedBrowserInfo == null || webOrigins.isEmpty()) {
             // Security assumption: If a trusted browser includes no web origin in the provided
             // AssistStructure, then the form is a native browser form (e.g. for a sync password).
             // TODO: Support WebViews in apps via Digital Asset Links
             // See: https://developer.android.com/reference/android/service/autofill/AutofillService#web-security
             return FormOrigin.App(appPackage)
         }
-        return when (browserMultiOriginMethod) {
+        return when (trustedBrowserInfo.multiOriginMethod) {
             BrowserMultiOriginMethod.None -> {
                 // Security assumption: If a browser is trusted but does not support tracking
                 // multiple origins, it is expected to annotate a single field, in most cases its