Add the API to support webview printing

Bug: 10190508
Change-Id: I47fc46bb1ea632876048b29621843f781c47aab7

core/java/android/webkit/WebView.java

@@ -48,6 +48,7 @@ import android.widget.AbsoluteLayout;
 
 import java.io.BufferedWriter;
 import java.io.File;
+import java.io.OutputStream;
 import java.util.Map;
 
 /**
@@ -1033,6 +1034,34 @@ public class WebView extends AbsoluteLayout
         return mProvider.capturePicture();
     }
 
+    /**
+     * Exports the contents of this Webview as PDF. Only supported for API levels
+     * {@link android.os.Build.VERSION_CODES#KEY_LIME_PIE} and above.
+     *
+     * @param out            The stream to export the PDF contents to. Cannot be null.
+     * @param width          The page width. Should be larger than 0.
+     * @param height         The page height. Should be larger than 0.
+     * @param resultCallback A callback to be invoked when the PDF content is exported.
+     *                       A true indicates success, and a false failure.
+     *
+     * TODO: explain method parameters, margins, consider making the callback
+     * return more meaningful information, explain any threading concerns, HW
+     * draw limitations, and make it public.
+     * TODO: at the moment we are asking app to provide paper size information (width
+     * and height). This is likely not ideal (I think need margin info too).
+     * Another approach would be using PrintAttributes. This is to be clarified later.
+     *
+     * TODO: explain this webview will not draw during export (onDraw will clear to
+     * background color) so recommend taking it offscreen, or putting in a layer with an
+     * overlaid progress UI / spinner.
+     * @hide
+     */
+    public void exportToPdf(OutputStream out, int width, int height,
+            ValueCallback<Boolean> resultCallback) {
+        checkThread();
+        mProvider.exportToPdf(out, width, height, resultCallback);
+    }
+
     /**
      * Gets the current scale of this WebView.
      *

core/java/android/webkit/WebViewClassic.java

@@ -2891,6 +2891,17 @@ public final class WebViewClassic implements WebViewProvider, WebViewProvider.Sc
         return result;
     }
 
+    /**
+     * See {@link WebView#exportToPdf()}
+     */
+    @Override
+    public void exportToPdf(java.io.OutputStream out, int width, int height,
+            ValueCallback<Boolean> resultCallback) {
+        // K-only API not implemented in WebViewClassic.
+        throw new IllegalStateException("This API not supported in Classic WebView.");
+
+    }
+
     /**
      * See {@link WebView#getScale()}
      */

core/java/android/webkit/WebViewProvider.java

@@ -40,6 +40,7 @@ import android.webkit.WebView.PictureListener;
 
 import java.io.BufferedWriter;
 import java.io.File;
+import java.io.OutputStream;
 import java.util.Map;
 
 /**
@@ -146,6 +147,9 @@ public interface WebViewProvider {
 
     public Picture capturePicture();
 
+    public void exportToPdf(OutputStream out, int width, int height,
+            ValueCallback<Boolean> resultCallback);
+
     public float getScale();
 
     public void setInitialScale(int scaleInPercent);