[Android WebView] Synthesize a fake page loading event on page source modification

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..0689b6582692cf61d88987ab8f9e9d4db3b1085e 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) == InvalidateTypes.URL
+                && mAwContents.hasPageScriptAccessedInitialDocument()) {
+            String url = mAwContents.getUrl();
+            final String aboutBlank = "about:blank";
+            url = TextUtils.isEmpty(url) ? aboutBlank : url;

[Charlie Reis, 2015/02/23 21:28:04]

I'm concerned about this code being different from desktop Chrome.  It seems
like we should just be resetting the address bar to GetVisibleEntry.  Making
this specific to about:blank seems different and potentially risky.

What's the reason we can't do the same thing as in desktop Chrome?  If we need
to diverge, we should carefully reason about this.

[mnaganov (inactive), 2015/02/23 22:17:55]

I'll double-check, if we are allowed to pass null urls to clients. I'm afraid,
we can't, that's why I have added this conversion.

In fact, GetVisibleEntry is what we retrieve under the hood. This is the
sequence of calls: AwContents.getUrl() -> WebContents.getUrl() [Java] ->
WebContentsAndroid::GetURL() [C++] -> WebContentsImpl::GetURL() ->
GetVisibleEntry()->GetVirtualURL() 
 
So I guess, we are not diverging beyond what is required to conform to WebView
API.

As for the reason, why we send events only for blank URLs, is to reduce
possibility of synthesizing superfluous events that will confuse clients.

Do you think there are any other URLs besides empty / about:blank that should be
considered here? 

[mnaganov (inactive), 2015/02/24 11:28:42]

I have checked that when executing WebView.loadUrl(""), onPageFinished receives
"about:blank", and this is what we should emulate here, so the conversion is
correct.
 

[Charlie Reis, 2015/02/24 19:37:55]

Sure, I'm not concerned about rewriting "" to about:blank.
I'm concerned about making the notification specific to about:blank, since
that's not really what GetVisibleEntry is doing.  I think it happens to be the
case that this will work, but it feels fragile to me.

GetVisibleEntry is returning the last committed entry if it's not safe to show
the pending entry.  In the HasAccessedInitialDocument case, I *think* the last
committed entry will always be about:blank.  If those ever differ, we'll be
reporting the wrong URL here.

Is it possible to change this code to use WebContents::GetLastCommittedURL()
instead?  We might be able to assert that it's equal to about:blank if that
matters, but it's closer to the intent of the spoof defense.

+            if (aboutBlank.equals(url)) {
+                mContentsClient.onPageStarted(url);
+                mContentsClient.onLoadResource(url);
+                mContentsClient.onProgressChanged(100);
+                mContentsClient.onPageFinished(url);
+            }
+        }
+    }
+
+    @Override
     public void toggleFullscreenModeForTab(boolean enterFullscreen) {
         if (enterFullscreen) {
             mContentViewClient.enterFullscreen();