[Microsoft.Android.Sdk.ILLink] fix crash when TZ changes (#7956)

Fixes: https://github.com/xamarin/xamarin-android/issues/7953

Context: 11f0e1bf64

When a timezone changes in a `Release` config app, it can crash with:

	[monodroid] Unable to find Android.Runtime.AndroidEnvironment.NotifyTimeZoneChanged()!

In commit 11f0e1b, we removed the line:

	<?xml version="1.0" encoding="utf-8" ?>
	<linker>
	    <assembly fullname="Mono.Android">
	--      <type fullname="Android.Runtime.AndroidEnvironment" />

Unfortunately, `AndroidEnvironment.NotifyTimeZoneChanged()` is called
from non-managed code, via:

  * The `NotifyTimeZoneChanges` broadcast receiver
    (in `src/java-runtime/java/mono/android/app/NotifyTimeZoneChanges.java`)
    which calls-
  * The `Rutime.notifyTimeZoneChanged()` `native` method
    (in `src/java-runtime/java/mono/android/Runtime.java`),
    implemented in-
  * `Java_mono_android_Runtime_notifyTimeZoneChanged()`
    (in`src/monodroid/jni/timezones.cc`).

The managed linker cannot "see" any of these references, so we
need to *always* preserve this method, as it is always callable.

Update `src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml`
so that `Android.Runtime.AndroidEnvironment.NotifyTimeZoneChanged()`
is always preserved.

Added a test for this scenario.

TODO: we may want to audit all `mono_class_get_method_from_name()`
calls and add more tests cases.

I also cleaned up the tests a bit with a `getResource()` local function.

src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml

@@ -2,6 +2,9 @@
 <linker>
 	<assembly fullname="Mono.Android">
 		<type fullname="Android.Runtime.AnnotationAttribute" />
+		<type fullname="Android.Runtime.AndroidEnvironment">
+			<method name="NotifyTimeZoneChanged" />
+		</type>
 		<type fullname="Android.Runtime.IJavaObject" />
 		<type fullname="Android.Runtime.InputStreamAdapter" preserve="methods" />
 		<type fullname="Android.Runtime.InputStreamInvoker" preserve="methods" />

tests/MSBuildDeviceIntegration/Resources/LinkDescTest/MainActivityReplacement.cs

@@ -115,6 +115,9 @@ namespace UnnamedProject
 			// [Test] Post
 			Android.Util.Log.Info(TAG, HttpClientTest.Post ());
 
+			// [Test] MethodsArePreserved
+			Android.Util.Log.Info (TAG, PreserveTest.MethodsArePreserved ());
+
 			// [Test] TextChanged
 			Android.Util.Log.Info (TAG, MaterialTextChanged.TextChanged (this));
 

tests/MSBuildDeviceIntegration/Resources/LinkDescTest/PreserveTest.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Reflection;
+
+public class PreserveTest
+{
+	// [Test]
+	public static string MethodsArePreserved ()
+	{
+		try {
+			// See src/monodroid/jni/timezones.cc for usage
+			var androidEnvironment = Type.GetType ("Android.Runtime.AndroidEnvironment, Mono.Android", throwOnError: true);
+			var notifyTimeZoneChanged = androidEnvironment.GetMethod ("NotifyTimeZoneChanged", BindingFlags.Static | BindingFlags.NonPublic);
+			if (notifyTimeZoneChanged == null) {
+				return $"[FAIL] {nameof (PreserveTest)}.{nameof (MethodsArePreserved)} FAILED: {nameof (notifyTimeZoneChanged)} is null)";
+			}
+			notifyTimeZoneChanged.Invoke (null, null);
+			return $"[PASS] {nameof (PreserveTest)}.{nameof (MethodsArePreserved)}";
+		} catch (Exception ex) {
+			return $"[FAIL] {nameof (PreserveTest)}.{nameof (MethodsArePreserved)} FAILED: {ex}";
+		}
+	}
+}

tests/MSBuildDeviceIntegration/Tests/InstallAndRunTests.cs

@@ -400,22 +400,16 @@ namespace Library1 {
 				},
 				Sources = {
 					new BuildItem.Source ("Bug21578.cs") {
-						TextContent = () => {
-							using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ("Xamarin.Android.Build.Tests.Resources.LinkDescTest.Bug21578.cs")))
-								return sr.ReadToEnd ();
-						},
+						TextContent = () => getResource("Bug21578")
 					},
 					new BuildItem.Source ("Bug35195.cs") {
-						TextContent = () => {
-							using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ("Xamarin.Android.Build.Tests.Resources.LinkDescTest.Bug35195.cs")))
-								return sr.ReadToEnd ();
-						},
+						TextContent = () => getResource("Bug35195")
 					},
 					new BuildItem.Source ("HttpClientTest.cs") {
-						TextContent = () => {
-							using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ("Xamarin.Android.Build.Tests.Resources.LinkDescTest.HttpClientTest.cs")))
-								return sr.ReadToEnd ();
-						},
+						TextContent = () => getResource("HttpClientTest")
+					},
+					new BuildItem.Source ("PreserveTest.cs") {
+						TextContent = () => getResource("PreserveTest")
 					},
 				},
 			};
@@ -424,10 +418,7 @@ namespace Library1 {
 				// DataContractSerializer is not trimming safe
 				// https://github.com/dotnet/runtime/issues/45559
 				lib2.Sources.Add (new BuildItem.Source ("Bug36250.cs") {
-					TextContent = () => {
-						using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ("Xamarin.Android.Build.Tests.Resources.LinkDescTest.Bug36250.cs")))
-							return sr.ReadToEnd ();
-					},
+					TextContent = () => getResource ("Bug36250")
 				});
 			}
 
@@ -450,10 +441,7 @@ namespace Library1 {
 				},
 				Sources = {
 					new BuildItem.Source ("MaterialTextChanged.cs") {
-						TextContent = () => {
-							using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ("Xamarin.Android.Build.Tests.Resources.LinkDescTest.MaterialTextChanged.cs")))
-								return sr.ReadToEnd ();
-						},
+						TextContent = () => getResource ("MaterialTextChanged")
 					},
 				},
 				OtherBuildItems = {
@@ -512,6 +500,12 @@ namespace Library1 {
 				StringAssert.Contains ("[LINKALLPASS]", logcatOutput);
 				StringAssert.DoesNotContain ("[LINKALLFAIL]", logcatOutput);
 			}
+
+			string getResource (string name)
+			{
+				using (var sr = new StreamReader (typeof (InstallAndRunTests).Assembly.GetManifestResourceStream ($"Xamarin.Android.Build.Tests.Resources.LinkDescTest.{name}.cs")))
+					return sr.ReadToEnd ();
+			}
 		}
 
 		[Test]