media/gpu/v4l2vda: Execute NotifyFlushDone for Flush if input stream is off

VDA client can request Flush() after Reset() and waits for NotifyFlushDone().
After FinishReset() is done, input stream becomes off. Even doing V4L2_DEC_CMD_STOP
at this time, the buffer with V4L2_BUF_FLAG_LAST will never be returned from
driver. As a result, NotifyFlushDone() will not be invoked and client waits
permanently.
To avoid this, V4L2VDA is changed as it tries to call NotifyFlushDone if input
stream is off.

BUG=chromium:833223, chromium:833221
TEST=Change resolution manually on crosvideo.appspot.com
TEST=VDA unittest on hana
TEST=CtsMediaTestCases on hana

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: I4245bdcee1e537dc7061e7833530ae59fc4aecb7
Reviewed-on: https://chromium-review.googlesource.com/1013802
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Cr-Commit-Position: refs/branch-heads/3396@{#67}
Cr-Branched-From: 9ef2aa8-refs/heads/master@{#550428}

Author: rosetta-jpn

media/gpu/v4l2/v4l2_video_decode_accelerator.cc

@@ -1275,11 +1275,13 @@ void V4L2VideoDecodeAccelerator::Enqueue() {
         input_ready_queue_.pop();
         free_input_buffers_.push_back(buffer);
         input_record.input_id = -1;
-        if (coded_size_.IsEmpty()) {
-          // If coded_size_.IsEmpty(), no output buffer could have been
+        if (coded_size_.IsEmpty() || !input_streamon_) {
+          // (1) If coded_size_.IsEmpty(), no output buffer could have been
           // allocated and there is nothing to flush. We can NotifyFlushDone()
           // immediately, without requesting flush to the driver via
           // SendDecoderCmdStop().
+          // (2) If input stream is off, we will never get the output buffer
+          // with V4L2_BUF_FLAG_LAST. We should NotifyFlushDone().
           NotifyFlushDoneIfNeeded();
         } else if (!SendDecoderCmdStop()) {
           return;