Add frame-count assertion to VpxVideoDecoderTest to diagnose flakes.

Bug: 864458
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ia2f18a1fc92a35d0a09cde3ad4f42e4c2e7936a4
Reviewed-on: https://chromium-review.googlesource.com/1140362Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575718}

media/filters/vpx_video_decoder_unittest.cc

@@ -332,6 +332,7 @@ TEST_F(VpxVideoDecoderTest, MemoryPoolAllowsMultipleDisplay) {
 #if !defined(OS_ANDROID)
   // Android doesn't seem to expose this bug, but the rest of the test is still
   // reasonable to complete even on Android.
+  ASSERT_EQ(output_frames_.size(), 26u);
   EXPECT_EQ(last_frame->data(VideoFrame::kYPlane),
             dupe_frame->data(VideoFrame::kYPlane));
   EXPECT_EQ(last_frame->data(VideoFrame::kUPlane),