[AW][ComponentUpdater] Override Service#onStartCommand for testing

Override AwComponentUpdateService#onStartCommand to run the native
update service. This way it's possible to deterministically force
launch the service on devices running android M and below for
testing purposes where it's not possible to force launch the job
service via `adb shell cmd jobscheduler`.

The service isn't exported so other apps can't start the service.

The service can be launched using the commandline:
`adb shell am startservice <webview-package-name>/org.chromium.android_webview.nonembedded.AwComponentUpdateService`

Fixed: 1209275
Test: Manually launch the service via adb, run webview shell and see scheduled jobs
Change-Id: I994b46e5b250e4f42498dc20b4b89c11ea452485
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2905562
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Hazem Ashmawy <hazems@chromium.org>
Cr-Commit-Position: refs/heads/master@{#894619}

android_webview/nonembedded/java/src/org/chromium/android_webview/nonembedded/AwComponentUpdateService.java

@@ -6,6 +6,7 @@ package org.chromium.android_webview.nonembedded;
 import android.app.job.JobParameters;
 import android.app.job.JobService;
 import android.content.Context;
+import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.SystemClock;
 
@@ -48,8 +49,65 @@ public class AwComponentUpdateService extends JobService {
     private static final String SHARED_PREFERENCES_NAME = "AwComponentUpdateServicePreferences";
     private static final String KEY_UNEXPECTED_EXIT = "UnexpectedExit";
 
+    /**
+     * The service can be both started by {@link android.app.job.JobScheduler} as a {@link
+     * JobService} and as a started service by calling {@link Context#startService}. These two
+     * states can apply at the same time. The service won't stop until all necessary stop
+     * methods are called:
+     * - Calling jobFinished if it's launched as a JobService.
+     * - Calling stopSelf if it's launched as a start service.
+     */
+    // If it has a non zero value, then the service is running via onStartCommand.
+    private int mServiceStartedId;
+
+    // If not null then the service is running as a Job service.
+    private JobParameters mJobParameters;
+
+    private boolean isServiceRunning() {
+        return mJobParameters != null || mServiceStartedId != 0;
+    }
+
+    // Called by JobScheduler.
     @Override
     public boolean onStartJob(JobParameters params) {
+        assert mJobParameters == null;
+        mJobParameters = params;
+        if (isServiceRunning()) {
+            return true;
+        }
+        return startNativeService();
+    }
+
+    // Called by JobScheduler.
+    @Override
+    public boolean onStopJob(JobParameters params) {
+        setUnexpectedExit(false);
+        mJobParameters = null;
+
+        // This should only be called if the service needs to be shut down before we've called
+        // jobFinished. Request reschedule so we can finish downloading component updates.
+        return /*reschedule= */ true;
+    }
+
+    // For testing only. To manually start the service on Android builds <= M where force running
+    // the job service doesn't work. The service isn't exported, so other apps won't be able to
+    // force start the service.
+    // Note: This can be simpilified when we stop supporting Android M in WebView (no need to store
+    // the state of how the service is running) or when manually starting the service on M isn't
+    // needed.
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        if (!isServiceRunning() && !startNativeService()) {
+            stopSelf(startId);
+        } else {
+            // Always keep the most recent startId as this is the one that should be used to stop
+            // the service.
+            mServiceStartedId = startId;
+        }
+        return START_STICKY;
+    }
+
+    private boolean startNativeService() {
         maybeRecordUnexpectedExit();
 
         // TODO(http://crbug.com/1179297) look at doing this in a task on a background thread
@@ -62,8 +120,8 @@ public class AwComponentUpdateService extends JobService {
                 recordJobDuration(SystemClock.uptimeMillis() - startTime);
                 recordFilesChanged(count);
                 recordDirectorySize();
-                jobFinished(params, /* needReschedule= */ false);
                 setUnexpectedExit(false);
+                stopService();
             });
             return true;
         }
@@ -71,13 +129,18 @@ public class AwComponentUpdateService extends JobService {
         return false;
     }
 
-    @Override
-    public boolean onStopJob(JobParameters params) {
-        setUnexpectedExit(false);
-
-        // This should only be called if the service needs to be shut down before we've called
-        // jobFinished. Request reschedule so we can finish downloading component updates.
-        return /*reschedule= */ true;
+    // Call the appropriate stop method according to how the service is launched.
+    private void stopService() {
+        // Service is launched as a started service.
+        if (mServiceStartedId > 0) {
+            stopSelf(mServiceStartedId);
+            mServiceStartedId = 0;
+        }
+        // Service is launched as a job service.
+        if (mJobParameters != null) {
+            jobFinished(mJobParameters, /* needReschedule= */ false);
+            mJobParameters = null;
+        }
     }
 
     private void recordDirectorySize() {