[Android WebView] Send WebChromeClient.onReceivedTitle when navigating back

The usual channel for delivering onReceivedTitle (via updating title for
a NavigationEntry) doesn't work in the case of history navigations, because
WebContentsImpl silences no-op updates of entries titles.

Chrome Browser uses another event for updating the title in this case --
via WebContentsDelegate::LoadingStateChanged. This patch enables WebView to
use it as well.

Note that WebChromeClient.onReceivedIcon doesn't need to be re-sent, as
nobody seems to bother checking whether the icon update is a "no-op", so
updates on history navigations just work.

BUG=481570

Review URL: https://codereview.chromium.org/1126383005

Cr-Commit-Position: refs/heads/master@{#329408}

android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegate.java

@@ -41,4 +41,9 @@ public abstract class AwWebContentsDelegate extends WebContentsDelegateAndroid {
     @Override
     @CalledByNative
     public abstract void navigationStateChanged(int flags);
+
+    // Not an override, because WebContentsDelegateAndroid maps this call
+    // into onLoad{Started|Stopped}.
+    @CalledByNative
+    public abstract void loadingStateChanged();
 }

android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java

@@ -271,6 +271,11 @@ class AwWebContentsDelegateAdapter extends AwWebContentsDelegate {
         }
     }
 
+    @Override
+    public void loadingStateChanged() {
+        mContentsClient.onReceivedTitle(mAwContents.getTitle());
+    }
+
     private static class GetDisplayNameTask extends AsyncTask<Void, Void, String[]> {
         final int mProcessId;
         final int mRenderId;

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

@@ -320,4 +320,23 @@ public class NavigationHistoryTest extends AwTestBase {
             }
         });
     }
+
+    // See http://crbug.com/481570
+    @SmallTest
+    public void testTitleUpdatedWhenGoingBack() throws Throwable {
+        final TestCallbackHelperContainer.OnPageFinishedHelper onPageFinishedHelper =
+                mContentsClient.getOnPageFinishedHelper();
+        NavigationHistory list = getNavigationHistory(mAwContents);
+        assertEquals(0, list.getEntryCount());
+
+        final String page1Url = addPage1ToServer(mWebServer);
+        final String page2Url = addPage2ToServer(mWebServer);
+
+        loadUrlSync(mAwContents, onPageFinishedHelper, page1Url);
+        loadUrlSync(mAwContents, onPageFinishedHelper, page2Url);
+        assertEquals(PAGE_2_TITLE, mContentsClient.getUpdatedTitle());
+        HistoryUtils.goBackSync(getInstrumentation(), mAwContents.getWebContents(),
+                onPageFinishedHelper);
+        assertEquals(PAGE_1_TITLE, mContentsClient.getUpdatedTitle());
+    }
 }

android_webview/native/aw_web_contents_delegate.cc

@@ -204,6 +204,18 @@ void AwWebContentsDelegate::ActivateContents(WebContents* contents) {
   }
 }
 
+void AwWebContentsDelegate::LoadingStateChanged(WebContents* source,
+                                                bool to_different_document) {
+  // Page title may have changed, need to inform the embedder.
+  // |source| may be null if loading has started.
+  JNIEnv* env = AttachCurrentThread();
+
+  ScopedJavaLocalRef<jobject> java_delegate = GetJavaDelegate(env);
+  if (java_delegate.obj()) {
+    Java_AwWebContentsDelegate_loadingStateChanged(env, java_delegate.obj());
+  }
+}
+
 void AwWebContentsDelegate::RequestMediaAccessPermission(
     WebContents* web_contents,
     const content::MediaStreamRequest& request,

android_webview/native/aw_web_contents_delegate.h

@@ -50,6 +50,8 @@ class AwWebContentsDelegate
 
   void CloseContents(content::WebContents* source) override;
   void ActivateContents(content::WebContents* contents) override;
+  void LoadingStateChanged(content::WebContents* source,
+                           bool to_different_document) override;
   void RequestMediaAccessPermission(
       content::WebContents* web_contents,
       const content::MediaStreamRequest& request,