add RunAllPendingInMessageLoop() after surface Commit

It turned out that some X11 events arrive to the surfaces when
the tests run with Xvfb (without -noreset flag), and that causes
additional events which causes mismatches on mock expectations
(especially on OnPointerFrame). RunAllPendingInMessageLoop()
will consume such events, so those failure won't happen again.

BUG=854674
TEST=exo_unittests with Xvfb :9 -nolisten tcp -screen 0 1280x800x24

Change-Id: I2c40aa29708362bd8eb4d05dd6448948622cfd81
Reviewed-on: https://chromium-review.googlesource.com/1105492Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Commit-Queue: Jun Mukai <mukai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568956}

components/exo/pointer_unittest.cc

@@ -27,8 +27,6 @@
 namespace exo {
 namespace {
 
-using PointerTest = test::ExoTestBase;
-
 class MockPointerDelegate : public PointerDelegate {
  public:
   MockPointerDelegate() {}
@@ -46,6 +44,22 @@ class MockPointerDelegate : public PointerDelegate {
   MOCK_METHOD0(OnPointerFrame, void());
 };
 
+class PointerTest : public test::ExoTestBase {
+ public:
+  PointerTest() = default;
+
+  void SetUp() override {
+    test::ExoTestBase::SetUp();
+    // Sometimes underlying infra (i.e. X11 / Xvfb) may emit pointer events
+    // which can break MockPointerDelegate's expectations, so they should be
+    // consumed before starting. See https://crbug.com/854674.
+    RunAllPendingInMessageLoop();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PointerTest);
+};
+
 TEST_F(PointerTest, SetCursor) {
   std::unique_ptr<Surface> surface(new Surface);
   std::unique_ptr<ShellSurface> shell_surface(new ShellSurface(surface.get()));