Run the later parts of startup as UI thread tasks

android_webview/lib/main/aw_main_delegate.cc

Index: android_webview/lib/main/aw_main_delegate.cc
diff --git a/android_webview/lib/main/aw_main_delegate.cc b/android_webview/lib/main/aw_main_delegate.cc
index aeef23c75e22b80f8c3061cbd682abe4126e40bf..125dc64e1aa86e4f81a58fdb0ab722256332039f 100644
--- a/android_webview/lib/main/aw_main_delegate.cc
+++ b/android_webview/lib/main/aw_main_delegate.cc
@@ -20,6 +20,7 @@
 #include "content/public/browser/browser_main_runner.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
+#include "content/public/common/startup_task_runner.h"
 #include "gpu/command_buffer/client/gl_in_process_context.h"
 #include "webkit/common/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h"
 
@@ -72,8 +73,18 @@ int AwMainDelegate::RunProcess(
   if (process_type.empty()) {
     AwBrowserDependencyFactoryImpl::InstallInstance();
 
+    // In Webview we must run all startup tasks immediately, since applications
+    // may depend on startup being complete on return from this function (or,
+    // to be precise, its callers from Java).
+    scoped_refptr<content::StartupTaskRunner> startup_task_runner(
+        new content::StartupTaskRunner(content::StartupTaskRunner::IMMEDIATE,
+                                       GetStartupObserver()));
+
     browser_runner_.reset(content::BrowserMainRunner::Create());
-    int exit_code = browser_runner_->Initialize(main_function_params);
+
+    int exit_code =
+        browser_runner_->Initialize(main_function_params, startup_task_runner);
+
     DCHECK(exit_code < 0);
 
     g_allow_wait_in_ui_thread.Get().reset(