For #9144 - Ignore previous Intent if activity is started from Recents

We'll now clearly differentiate between cold / hot starts of HomeActivity.kt.
This is needed because Android will resend the original Intent which initially
started the Activity whenever it is restarted from the Recents Screen if the
activity is already destroyed at that time. So in the event that the activity
was before started with an Intent to open a webpage for example whenever the
activity is restarted from Recents it will receive the same Intent to open a
webpage even though that Intent has already been consumed.

Activity's onCreate() will only use the intent processors when the activity is
cold started so that we'll only initially act upon Intents configured for
different behaviors inside the app.
If the activity is destroyed while in background and opened from Recents it
will not act upon the original Intent which is now resent by Android.

Activity's onNewIntent() will be called to act upon a new Intent if the
activity is hot started since we are declared as singleTask and it now has the
responsibility to delegate various intent processors to consume that Intent.

app/src/main/java/org/mozilla/fenix/HomeActivity.kt

@@ -154,7 +154,9 @@ open class HomeActivity : LocaleAwareAppCompatActivity() {
 
         sessionObserver = UriOpenedObserver(this)
 
-        externalSourceIntentProcessors.any { it.process(intent, navHost.navController, this.intent) }
+        if (isActivityColdStarted(intent, savedInstanceState)) {
+            externalSourceIntentProcessors.any { it.process(intent, navHost.navController, this.intent) }
+        }
 
         Performance.processIntentIfPerformanceTest(intent, this)
 
@@ -476,6 +478,15 @@ open class HomeActivity : LocaleAwareAppCompatActivity() {
         this.visualCompletenessQueue = visualCompletenessQueue
     }
 
+    @VisibleForTesting
+    internal fun isActivityColdStarted(startingIntent: Intent, activityIcicle: Bundle?): Boolean =
+        // First time opening this activity in the task.
+        // Cold start / start from Recents after back press.
+        activityIcicle == null &&
+        // Activity was restarted from Recents after it was destroyed by Android while in background
+        // in cases of memory pressure / "Don't keep activities".
+        startingIntent.flags and Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY == 0
+
     companion object {
         const val OPEN_TO_BROWSER = "open_to_browser"
         const val OPEN_TO_BROWSER_AND_LOAD = "open_to_browser_and_load"

app/src/test/java/org/mozilla/fenix/HomeActivityTest.kt

@@ -5,11 +5,14 @@
 package org.mozilla.fenix
 
 import android.content.Intent
+import android.os.Bundle
 import mozilla.components.support.test.robolectric.testContext
 import mozilla.components.support.utils.toSafeIntent
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
 import org.junit.Assert.assertNotEquals
 import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.mozilla.fenix.HomeActivity.Companion.PRIVATE_BROWSING_MODE
@@ -58,4 +61,38 @@ class HomeActivityTest {
         assertNotEquals(testContext.settings().lastKnownMode, activity.getModeFromIntentOrLastKnown(intent))
         assertEquals(BrowsingMode.Private, activity.getModeFromIntentOrLastKnown(intent))
     }
+
+    @Test
+    fun `isActivityColdStarted returns true for null savedInstanceState and not launched from history`() {
+        val activity = HomeActivity()
+
+        assertTrue(activity.isActivityColdStarted(Intent(), null))
+    }
+
+    @Test
+    fun `isActivityColdStarted returns false for valid savedInstanceState and not launched from history`() {
+        val activity = HomeActivity()
+
+        assertFalse(activity.isActivityColdStarted(Intent(), Bundle()))
+    }
+
+    @Test
+    fun `isActivityColdStarted returns false for null savedInstanceState and launched from history`() {
+        val activity = HomeActivity()
+        val startingIntent = Intent().apply {
+            flags = flags or Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY
+        }
+
+        assertFalse(activity.isActivityColdStarted(startingIntent, null))
+    }
+
+    @Test
+    fun `isActivityColdStarted returns false for null savedInstanceState and not launched from history`() {
+        val activity = HomeActivity()
+        val startingIntent = Intent().apply {
+            flags = flags or Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY
+        }
+
+        assertFalse(activity.isActivityColdStarted(startingIntent, Bundle()))
+    }
 }