[Android WebView] Synthesize a fake page loading event on page source modification (Re-land)

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

Index: android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java b/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
index 3f2c707dce8447bc8b0abc5a24dc508ac6b8c1b2..5e37d992ca24f1353d006c4381410dfc10e1f31c 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java
@@ -11,6 +11,7 @@ import android.os.AsyncTask;
 import android.os.Handler;
 import android.os.Message;
 import android.provider.MediaStore;
+import android.text.TextUtils;
 import android.util.Log;
 import android.view.KeyEvent;
 import android.view.View;
@@ -19,6 +20,7 @@ import android.webkit.ValueCallback;
 
 import org.chromium.base.ContentUriUtils;
 import org.chromium.base.ThreadUtils;
+import org.chromium.content_public.browser.InvalidateTypes;
 
 /**
  * Adapts the AwWebContentsDelegate interface to the AwContentsClient interface.
@@ -213,6 +215,22 @@ class AwWebContentsDelegateAdapter extends AwWebContentsDelegate {
     }
 
     @Override
+    public void navigationStateChanged(int flags) {
+        if ((flags & InvalidateTypes.URL) != 0
+                && mAwContents.hasAccessedInitialDocument()
+                && mAwContents.getDidAttemptLoad()) {

[Charlie Reis, 2015/03/02 23:09:31]

I don't think we need this, do we?  It seems like
NavigationController::GetPendingEntry() would tell you whether there's an
in-progress load or not.  (DidStartProvisionalLoad creates a pending entry.)

Is there a reason you need the "has there ever been a load" state, or is
GetPendingEntry() sufficient?  We won't have a visible URL to spoof if there
isn't a pending entry.  (GetVisibleEntry will just return the last committed
entry in that case.)

[mnaganov (inactive), 2015/03/03 08:55:48]

Indeed, my initial plan was to just use GetPendingEntry. Then I discovered that
WebContentsImpl::DidAccessInitialDocument discards the pending entry prior to
issuing  NavigationStateChanged notification, so when you check it here, it will
be null.

Then I tried to use the fact that NavigatorImpl::DidStartProvisionalLoad also
issues NavigationStateChanged notification immediately after creating the
pending entry, so I though I can catch it here, make a note to self via a
private flag, and then use this flag when I'll receive NavigationStateChanged
the second time due to a DOM mutation. But unfortunately, this approach was not
reliable due to asynchronous nature of notifications -- between the moment when
the pending entry has been set and the moment when this code receives
NavigationStateChanged, the pending entry could already had been discarded due
to a DOM mutation.

So I resorted to catching DidStartProvisionalLoadForFrame, which seems to work
reliably, as it's a synchronous callback.

+            // Hint the client to show the last committed url, as it may be unsafe to show
+            // the pending entry.
+            String url = mAwContents.getLastCommittedUrl();
+            url = TextUtils.isEmpty(url) ? "about:blank" : url;
+            mContentsClient.onPageStarted(url);
+            mContentsClient.onLoadResource(url);
+            mContentsClient.onProgressChanged(100);
+            mContentsClient.onPageFinished(url);
+        }
+    }
+
+    @Override
     public void toggleFullscreenModeForTab(boolean enterFullscreen) {
         if (enterFullscreen) {
             mContentViewClient.enterFullscreen();