[aw] Ensure that WebView APIs do not crash if called after destruction.

The documentation for WebView#destroy() reads "This method should be called
after this WebView has been removed from the view system. No other methods
may be called on this WebView after destroy". However, some apps do not
respect that restriction so this change ensures that we fail gracefully
in that case and do not crash.

BUG=415666

Review URL: https://codereview.chromium.org/581423002

Cr-Commit-Position: refs/heads/master@{#296029}

android_webview/java/src/org/chromium/android_webview/AwContentViewClient.java

@@ -60,7 +60,10 @@ public class AwContentViewClient extends ContentViewClient {
                     if (mAwContents.isFullScreen()) {
                         return;
                     }
-                    viewGroup.addView(mAwContents.enterFullScreen());
+                    View fullscreenView = mAwContents.enterFullScreen();
+                    if (fullscreenView != null) {
+                        viewGroup.addView(fullscreenView);
+                    }
                 }
             });
             mAwContentsClient.onShowCustomView(viewGroup, cb);

android_webview/javatests/src/org/chromium/android_webview/test/AwContentsTest.java

@@ -6,6 +6,7 @@ package org.chromium.android_webview.test;
 
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
+import android.graphics.Canvas;
 import android.os.Handler;
 import android.os.Looper;
 import android.os.Message;
@@ -13,16 +14,18 @@ import android.test.UiThreadTest;
 import android.test.suitebuilder.annotation.LargeTest;
 import android.test.suitebuilder.annotation.SmallTest;
 import android.util.Pair;
+import android.view.KeyEvent;
+import android.view.View;
 
 import org.apache.http.Header;
 import org.apache.http.HttpRequest;
-
 import org.chromium.android_webview.AwContents;
 import org.chromium.android_webview.AwSettings;
 import org.chromium.android_webview.test.TestAwContentsClient.OnDownloadStartHelper;
 import org.chromium.android_webview.test.util.CommonResources;
 import org.chromium.base.test.util.Feature;
 import org.chromium.content.browser.test.util.CallbackHelper;
+import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.net.test.util.TestWebServer;
 
 import java.io.InputStream;
@@ -92,6 +95,50 @@ public class AwContentsTest extends AwTestBase {
         }
     }
 
+    @SmallTest
+    @Feature({"AndroidWebView"})
+    @UiThreadTest
+    public void testWebViewApisFailGracefullyAfterDestruction() throws Throwable {
+        AwContents awContents =
+                createAwTestContainerView(mContentsClient).getAwContents();
+        awContents.destroy();
+
+        assertNull(awContents.getWebContents());
+        assertNull(awContents.getContentViewCore());
+        assertNull(awContents.getNavigationController());
+
+        // The documentation for WebView#destroy() reads "This method should be called
+        // after this WebView has been removed from the view system. No other methods
+        // may be called on this WebView after destroy".
+        // However, some apps do not respect that restriction so we need to ensure that
+        // we fail gracefully and do not crash when APIs are invoked after destruction.
+        // Due to the large number of APIs we only test a representative selection here.
+        awContents.clearHistory();
+        awContents.loadUrl(new LoadUrlParams("http://www.google.com"));
+        awContents.findAllAsync("search");
+        assertNull(awContents.getUrl());
+        assertNull(awContents.getContentSettings());
+        assertFalse(awContents.canGoBack());
+        awContents.disableJavascriptInterfacesInspection();
+        awContents.invokeZoomPicker();
+        awContents.onResume();
+        awContents.stopLoading();
+        awContents.onWindowVisibilityChanged(View.VISIBLE);
+        awContents.requestFocus();
+        awContents.isMultiTouchZoomSupported();
+        awContents.setOverScrollMode(View.OVER_SCROLL_NEVER);
+        awContents.pauseTimers();
+        awContents.onContainerViewScrollChanged(200, 200, 100, 100);
+        awContents.computeScroll();
+        awContents.onMeasure(100, 100);
+        awContents.onDraw(new Canvas());
+        awContents.getMostRecentProgress();
+        assertEquals(0, awContents.computeHorizontalScrollOffset());
+        assertEquals(0, awContents.getContentWidthCss());
+        awContents.onKeyUp(KeyEvent.KEYCODE_BACK,
+                new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MENU));
+    }
+
     @LargeTest
     @Feature({"AndroidWebView"})
     public void testCreateAndGcManyTimes() throws Throwable {