Add base::RunLoop and update ui_test_utils to use it to reduce flakiness

chrome/browser/ui/find_bar/find_bar_host_browsertest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/message_loop.h"
 #include "base/string16.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 732 matching lines @@
   TabContentsWrapper* tab = browser()->GetSelectedTabContentsWrapper();
 
   int moved_x_coord = FindInPageTillBoxMoves(tab, start_position.x(),
       L"Chromium", kMoveIterations);
   // The find box should have moved.
   EXPECT_TRUE(moved_x_coord != start_position.x());
 
   // Search for something guaranteed not to be obscured by the Find box.
   EXPECT_EQ(1, FindInPageWchar(tab, L"Done",
                                kFwd, kIgnoreCase, &ordinal));
+
+  // Drain MessageLoop so that find bar position settles.
+  ui_test_utils::RunAllPendingInMessageLoop();
+
   // Check the position.
   EXPECT_TRUE(GetFindBarWindowInfo(&position, &fully_visible));
   EXPECT_TRUE(fully_visible);
 
   // Make sure Find box has moved back to its original location.
   EXPECT_EQ(position.x(), start_position.x());
 
   // Move the find box again.
   moved_x_coord = FindInPageTillBoxMoves(tab, start_position.x(),
       L"Chromium", kMoveIterations);
   EXPECT_TRUE(moved_x_coord != start_position.x());
 
   // Search for an invalid string.
   EXPECT_EQ(0, FindInPageWchar(tab, L"WeirdSearchString",
                                kFwd, kIgnoreCase, &ordinal));
 
+  // Drain MessageLoop so that find bar position settles.
+  ui_test_utils::RunAllPendingInMessageLoop();
+
   // Check the position.
   EXPECT_TRUE(GetFindBarWindowInfo(&position, &fully_visible));
   EXPECT_TRUE(fully_visible);
 
   // Make sure Find box has moved back to its original location.
   EXPECT_EQ(position.x(), start_position.x());
 }
 
 #if defined(OS_MACOSX)
 // FindNextInNewTabUsesPrepopulate times-out, at least on Mac.
@@ skipping 465 matching lines @@
   ui_test_utils::RunAllPendingInMessageLoop();  // Needed on Linux.
   EXPECT_TRUE(GetFindBarWindowInfo(&position, NULL));
 
   ui_test_utils::NavigateToURLWithDisposition(
       browser(), url, NEW_FOREGROUND_TAB,
       ui_test_utils::BROWSER_TEST_WAIT_FOR_NAVIGATION);
   browser()->CloseTab();
   EXPECT_TRUE(GetFindBarWindowInfo(&position2, NULL));
   EXPECT_EQ(position, position2);
 }