Test: Un-hide the image drag content provider

Un-hide the content provider with adding a doc to make it ready for the next Androidx webkit release.

Relnote: Added Content provider to enable Image Drag out.

Bug: 255733242
Change-Id: Ib859b0b40affa7e0a4be4efe5cb9b219ceb13723

diff --git a/webkit/integration-tests/testapp/src/main/java/com/example/androidx/webkit/ImageDragActivity.java b/webkit/integration-tests/testapp/src/main/java/com/example/androidx/webkit/ImageDragActivity.java
index 1ae07c2..1569ff6 100644
--- a/webkit/integration-tests/testapp/src/main/java/com/example/androidx/webkit/ImageDragActivity.java
+++ b/webkit/integration-tests/testapp/src/main/java/com/example/androidx/webkit/ImageDragActivity.java

@@ -18,6 +18,7 @@
 
 import android.os.Bundle;
 import android.webkit.WebView;
+import android.webkit.WebViewClient;
 
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
@@ -33,6 +34,7 @@
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_image_drag);
         WebView demoWebview = findViewById(R.id.image_webview);
+        demoWebview.setWebViewClient(new WebViewClient()); // Open links in this WebView.
 
         demoWebview.loadUrl("www.google.com");
     }

diff --git a/webkit/webkit/api/current.txt b/webkit/webkit/api/current.txt
index faf13cb..0c9d5ee 100644
--- a/webkit/webkit/api/current.txt
+++ b/webkit/webkit/api/current.txt

@@ -5,6 +5,16 @@
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.GET_COOKIE_INFO, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public static java.util.List<java.lang.String!> getCookieInfo(android.webkit.CookieManager, String);
   }
 
+  public final class DropDataContentProvider extends android.content.ContentProvider {
+    ctor public DropDataContentProvider();
+    method public int delete(android.net.Uri, String?, String![]?);
+    method public String? getType(android.net.Uri);
+    method public android.net.Uri? insert(android.net.Uri, android.content.ContentValues?);
+    method public boolean onCreate();
+    method public android.database.Cursor? query(android.net.Uri, String![]?, String?, String![]?, String?);
+    method public int update(android.net.Uri, android.content.ContentValues?, String?, String![]?);
+  }
+
   public abstract class JavaScriptReplyProxy {
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.WEB_MESSAGE_LISTENER, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public abstract void postMessage(String);
   }

diff --git a/webkit/webkit/api/public_plus_experimental_current.txt b/webkit/webkit/api/public_plus_experimental_current.txt
index faf13cb..0c9d5ee 100644
--- a/webkit/webkit/api/public_plus_experimental_current.txt
+++ b/webkit/webkit/api/public_plus_experimental_current.txt

@@ -5,6 +5,16 @@
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.GET_COOKIE_INFO, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public static java.util.List<java.lang.String!> getCookieInfo(android.webkit.CookieManager, String);
   }
 
+  public final class DropDataContentProvider extends android.content.ContentProvider {
+    ctor public DropDataContentProvider();
+    method public int delete(android.net.Uri, String?, String![]?);
+    method public String? getType(android.net.Uri);
+    method public android.net.Uri? insert(android.net.Uri, android.content.ContentValues?);
+    method public boolean onCreate();
+    method public android.database.Cursor? query(android.net.Uri, String![]?, String?, String![]?, String?);
+    method public int update(android.net.Uri, android.content.ContentValues?, String?, String![]?);
+  }
+
   public abstract class JavaScriptReplyProxy {
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.WEB_MESSAGE_LISTENER, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public abstract void postMessage(String);
   }

diff --git a/webkit/webkit/api/restricted_current.txt b/webkit/webkit/api/restricted_current.txt
index faf13cb..0c9d5ee 100644
--- a/webkit/webkit/api/restricted_current.txt
+++ b/webkit/webkit/api/restricted_current.txt

@@ -5,6 +5,16 @@
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.GET_COOKIE_INFO, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public static java.util.List<java.lang.String!> getCookieInfo(android.webkit.CookieManager, String);
   }
 
+  public final class DropDataContentProvider extends android.content.ContentProvider {
+    ctor public DropDataContentProvider();
+    method public int delete(android.net.Uri, String?, String![]?);
+    method public String? getType(android.net.Uri);
+    method public android.net.Uri? insert(android.net.Uri, android.content.ContentValues?);
+    method public boolean onCreate();
+    method public android.database.Cursor? query(android.net.Uri, String![]?, String?, String![]?, String?);
+    method public int update(android.net.Uri, android.content.ContentValues?, String?, String![]?);
+  }
+
   public abstract class JavaScriptReplyProxy {
     method @RequiresFeature(name=androidx.webkit.WebViewFeature.WEB_MESSAGE_LISTENER, enforcement="androidx.webkit.WebViewFeature#isFeatureSupported") public abstract void postMessage(String);
   }

diff --git a/webkit/webkit/src/main/java/androidx/webkit/DropDataContentProvider.java b/webkit/webkit/src/main/java/androidx/webkit/DropDataContentProvider.java
index 6c38760..6af699c 100644
--- a/webkit/webkit/src/main/java/androidx/webkit/DropDataContentProvider.java
+++ b/webkit/webkit/src/main/java/androidx/webkit/DropDataContentProvider.java

@@ -25,7 +25,6 @@
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.annotation.RestrictTo;
 import androidx.webkit.internal.WebViewGlueCommunicator;
 
 import org.chromium.support_lib_boundary.DropDataContentProviderBoundaryInterface;
@@ -33,13 +32,23 @@
 import java.io.FileNotFoundException;
 
 /**
- * TODO(1353048): Un-hide this after finishing the feature.
+ * WebView provides partial support for Android
+ * <a href="https://developer.android.com/develop/ui/views/touch-and-input/drag-drop">
+ * Drag and Drop</a> allowing images, text and links to be dragged out of a WebView.
  *
- * @hide
- * This should be added to the manifest in order to enable dragging images out.
+ * The content provider is required to make the images drag work, to enable, you should add this
+ * class to your manifest, for example:
+ *
+ * <pre class="prettyprint">
+ *  &lt;provider
+ *             android:authorities="{{your package}}.DropDataProvider"
+ *             android:name="androidx.webkit.DropDataContentProvider"
+ *             android:exported="false"
+ *             android:grantUriPermissions="true"/&gt;
+ * </pre>
+ *
  */
-@RestrictTo(RestrictTo.Scope.LIBRARY)
-public class DropDataContentProvider extends ContentProvider {
+public final class DropDataContentProvider extends ContentProvider {
     DropDataContentProviderBoundaryInterface mImpl;
 
     @Override