Allow posting the CronetEngine UI Thread initialization on a custom Ui executor instead of the defa…

components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java

Index: components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
diff --git a/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java b/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
index 629b8d9e4b42347cf71cf62303b2960eb5997b0d..f97f6ee4a2100162b0552d652498636442a4e4f0 100644
--- a/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
+++ b/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
@@ -178,7 +178,11 @@ public class CronetUrlRequestContext extends CronetEngineBase {
         if (Looper.getMainLooper() == Looper.myLooper()) {
             task.run();
         } else {
-            new Handler(Looper.getMainLooper()).post(task);
+            if (builder.uiExecutor() != null) {
+                builder.uiExecutor().execute(task);
+            } else {
+                new Handler(Looper.getMainLooper()).post(task);
+            }
         }
     }