No fileEntry results returned on Android 6

I've got what appears to be a file read permissions issue in my Cordova app, but I can't for the life of me track it down properly. Between Android 5 and Android 6, I'm seeing completely different results to the same calls to fileEntry. Does anyone know whether there are needed changes to be able to read files/directories in Android > 5?

Gory details: I copied the code out to a helloWorld app with just cordova-plugin-file (calling cordova create hello), and am getting the same results. My changes are as follows:

I added a single element to the body of index.html:

        <div id="contents"></div>

I also changed the stock receivedEvent method in index.js, just to iterate through the various directories on the device and return what cordova-plugin-file gives me:

receivedEvent: function (id) {
    "use strict";

    var parentElement = document.getElementById(id),
        listeningElement = parentElement.querySelector('.listening'),
        receivedElement = parentElement.querySelector('.received'),
        localURLs    = [
            cordova.file.documentsDirectory,
            cordova.file.externalRootDirectory,
            cordova.file.sharedDirectory,
            cordova.file.syncedDataDirectory
        ],
        DirsRemaining = localURLs.length,
        i,
        contents = "",
        addFileEntry = function (entry) {
            var dirReader = entry.createReader();
            dirReader.readEntries(
                function (entries) {
                    var i;
                    for (i = 0; i < entries.length; i += 1) {
                        if (entries[i].isDirectory === true) {
                            contents += "<h2> Directory: " + entries[i].fullPath + "</h2>";
                            // Recursive -- call back into this subdirectory
                            DirsRemaining += 1;
                            addFileEntry(entries[i]);
                        } else {
                            contents += "<p> File: " + entries[i].fullPath + "</p>";
                        }
                    }
                    DirsRemaining -= 1;
                    if (DirsRemaining <= 0) {
                        if (contents.length > 0) {
                            document.getElementById("contents").innerHTML = contents;
                        } else {
                            // nothing to select -- inform the user
                            document.getElementById("contents").innerHTML = "No documents found";
                        }
                    }
                },
                function (error) {
                    console.log("readEntries error: " + error.code);
                    contents += "<p>readEntries error: " + error.code + "</p>";
                }
            );
        },
        addError = function (error) {
            // log the error and continue processing
            console.log("getDirectory error: " + error.code);
            DirsRemaining -= 1;
        };
    for (i = 0; i < localURLs.length; i += 1) {
        if (localURLs[i] === null || localURLs[i].length === 0) {
            DirsRemaining -= 1;
            continue; // skip blank / non-existent paths for this platform
        }
        window.resolveLocalFileSystemURL(localURLs[i], addFileEntry, addError);
    }

    listeningElement.setAttribute('style', 'display:none;');
    receivedElement.setAttribute('style', 'display:block;');

    console.log('Received Event: ' + id);
}

Possible security configurations:

My platforms/android/AndroidManifest.xml file contains the appropriate permissions:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Here's my CSP in index.html (it's just the stock one):

<meta http-equiv="Content-Security-Policy" content="default-src 'self' data: gap: https://ssl.gstatic.com 'unsafe-eval'; style-src 'self' 'unsafe-inline'; media-src *; img-src 'self' data: content:;">

---

Here are the results:

Android 5. Note directories and a file (there are others offscreen)

Android 6. Note that I have some files in the subdirectories under cordova.file.externalRootDirectory that should be displayed; it should also be displaying the subdirectories themselves.

Hat tip to @greenapps for the hint -- this behavior is apparently due to the runtime permissions introduced in Android 6.

For Cordova, there's a plugin that can address the issue until cordova-android is cleaned up a bit (as of 11/6/2017, PhoneGap Build uses cordova-android 6.2.3, which depends on cordova-plugin-compat to deal with this). My fix for now:

cordova plugin add cordova.plugins.diagnostic

Then the routine to add the appropriate runtime permissions:

// request read access to the external storage if we don't have it

cordova.plugins.diagnostic.getExternalStorageAuthorizationStatus(function (status) {
    if (status === cordova.plugins.diagnostic.permissionStatus.GRANTED) {
        console.log("External storage use is authorized");
    } else {
        cordova.plugins.diagnostic.requestExternalStorageAuthorization(function (result) {
           console.log("Authorization request for external storage use was " + (result === cordova.plugins.diagnostic.permissionStatus.GRANTED ? "granted" : "denied"));
       }, function (error) {
           console.error(error);
       });
   }
}, function (error) {
   console.error("The following error occurred: " + error);
});