Make PlatformAppBrowserTest....AdjustBoundsTo... not flaky

chrome/browser/apps/app_browsertest.cc

Index: chrome/browser/apps/app_browsertest.cc
diff --git a/chrome/browser/apps/app_browsertest.cc b/chrome/browser/apps/app_browsertest.cc
index 44e280485527da4cc2b1a380182b2e48e65b4552..436f75c30b52e92026c72ef5bfeba561144fa88f 100644
--- a/chrome/browser/apps/app_browsertest.cc
+++ b/chrome/browser/apps/app_browsertest.cc
@@ -750,8 +750,12 @@ IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest,
                        AppWindowAdjustBoundsToBeVisibleOnScreen) {
   // TODO(benwells): Remove this logging once flakiness has been observed.
   // See http://crbug.com/377754.
+  ExtensionTestMessageListener launched_listener("Launched", false);
+
   LOG(WARNING) << "Loading minimal app";
   const Extension* extension = LoadAndLaunchPlatformApp("minimal");
+  EXPECT_TRUE(launched_listener.WaitUntilSatisfied());
+
   LOG(WARNING) << "Creating window";
   AppWindow* window = CreateAppWindow(extension);