BarcodeDetector should be created on a background thread.

BarcodeDetector creation takes long time and triggers strict mode
violation warning therefore should be created on a worker thread.

Also some cleanup - new tab now can be created from worker thread as it
is launching an intent instead of going through tab manager.

Bug: 993920
Change-Id: Ic974ebe2cae41c7a82fca87976656335799f5ba6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2081615
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Reviewed-by: Tanya Gupta <tgupta@chromium.org>
Reviewed-by: Travis Skare <skare@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750641}

chrome/browser/share/android/java/src/org/chromium/chrome/browser/share/qrcode/scan_tab/QrCodeScanMediator.java

@@ -12,8 +12,6 @@ import android.content.pm.PackageManager;
 import android.graphics.ImageFormat;
 import android.hardware.Camera;
 import android.net.Uri;
-import android.os.Handler;
-import android.os.Looper;
 import android.os.Process;
 import android.provider.Browser;
 import android.util.SparseArray;
@@ -23,6 +21,7 @@ import com.google.android.gms.vision.Frame;
 import com.google.android.gms.vision.barcode.Barcode;
 import com.google.android.gms.vision.barcode.BarcodeDetector;
 
+import org.chromium.base.task.AsyncTask;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.ShortcutHelper;
@@ -43,16 +42,13 @@ public class QrCodeScanMediator implements Camera.PreviewCallback {
     /** Interface used for notifying in the event of navigation to a URL. */
     public interface NavigationObserver { void onNavigation(); }
 
-    /** Interface for creating and navigation to a new tab for a given URL. */
-    public interface TabCreator { void createNewTab(String url); }
-
     private final Context mContext;
     private final PropertyModel mPropertyModel;
-    private final BarcodeDetector mDetector;
     private final NavigationObserver mNavigationObserver;
-    private final Handler mMainThreadHandler;
     private final AndroidPermissionDelegate mPermissionDelegate;
 
+    private BarcodeDetector mDetector;
+
     /**
      * The QrCodeScanMediator constructor.
      *
@@ -66,9 +62,11 @@ public class QrCodeScanMediator implements Camera.PreviewCallback {
         mPermissionDelegate = new ActivityAndroidPermissionDelegate(
                 new WeakReference<Activity>((Activity) mContext));
         updatePermissionSettings();
-        mDetector = new BarcodeDetector.Builder(context).build();
         mNavigationObserver = observer;
-        mMainThreadHandler = new Handler(Looper.getMainLooper());
+
+        // Set detector to null until it gets initialized asynchronously.
+        mDetector = null;
+        initBarcodeDetectorAsync();
     }
 
     /** Returns whether the user has granted camera permissions. */
@@ -142,6 +140,10 @@ public class QrCodeScanMediator implements Camera.PreviewCallback {
      */
     @Override
     public void onPreviewFrame(byte[] data, Camera camera) {
+        if (mDetector == null) {
+            return;
+        }
+
         ByteBuffer buffer = ByteBuffer.allocate(data.length);
         buffer.put(data);
         Frame frame =
@@ -164,11 +166,8 @@ public class QrCodeScanMediator implements Camera.PreviewCallback {
             return;
         }
 
-        /** Tab creation should happen on the main thread. */
-        mMainThreadHandler.post(() -> {
-            openUrl(firstCode.rawValue);
-            mNavigationObserver.onNavigation();
-        });
+        openUrl(firstCode.rawValue);
+        mNavigationObserver.onNavigation();
     }
 
     private void openUrl(String url) {
@@ -183,4 +182,18 @@ public class QrCodeScanMediator implements Camera.PreviewCallback {
         IntentHandler.addTrustedIntentExtras(intent);
         mContext.startActivity(intent);
     }
+
+    private void initBarcodeDetectorAsync() {
+        new AsyncTask<BarcodeDetector>() {
+            @Override
+            protected BarcodeDetector doInBackground() {
+                return new BarcodeDetector.Builder(mContext).build();
+            }
+
+            @Override
+            protected void onPostExecute(BarcodeDetector detector) {
+                mDetector = detector;
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    }
 }