Fix race condition where not all logs would be added to the viewer.

debuglogs-viewer/lib/src/main/assets/debuglogs-viewer.js

@@ -220,6 +220,11 @@ function applyFilter() {
   editor.setValue(filtered, -1);
 }
 
+function appendLines(lines) {
+  editor.session.insert({ row: editor.session.getLength(), column: 0}, lines);
+  logLines += lines;
+}
+
 function readLines(offset, limit) {
   const lines = logLines.split("\n")
   if (offset >= lines.length) {

debuglogs-viewer/lib/src/main/java/org/signal/debuglogsviewer/DebugLogsViewer.kt

@@ -46,7 +46,11 @@ object DebugLogsViewer {
   fun appendLines(webview: WebView, lines: String) {
     // Set the debug log lines
     val escaped = JSONObject.quote(lines)
-    ThreadUtil.runOnMain { webview.evaluateJavascript("editor.insert($escaped); logLines+=$escaped;", null) }
+    val latch = CountDownLatch(1)
+    ThreadUtil.runOnMain {
+      webview.evaluateJavascript("appendLines($escaped)") { latch.countDown() }
+    }
+    latch.await()
   }
 
   @JvmStatic