media/gpu/VEAunittest: Lengthen the timeout of producing a bitstream buffer

VEA unittest fails if VEA cannot produce a bitstream buffer in three seconds
from the previous bitstream buffer. Three seconds seems sufficient but we see
the flakieness on low end devices. This CL lengthens timeout to 10 sec in order
to figure out if it is a real failure or just low performance.

Bug: 1019307
Test: None
Change-Id: I103d8e32fb444dbe2576db0af815714af7def49f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890450
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710834}

media/gpu/video_encode_accelerator_unittest.cc

@@ -126,10 +126,10 @@ const unsigned int kMinFramesForBitrateTests = 300;
 const unsigned int kLoggedLatencyPercentiles[] = {50, 75, 95};
 // Timeout between each BitstreamBufferReady() call and flush callback.
 // In the multiple encoder test case, the FPS might be lower than expected.
-// Currently the largest resolution we run at lab is 4K. The FPS of the slowest
-// device in MultipleEncoders test case is 3. Here we set the timeout 10x of the
-// expected period for margin.
-const unsigned int kBitstreamBufferReadyTimeoutMs = 3000;
+// To rule out a flakiness on low-end devices, the timeout is set to 10 sec,
+// https://crbug.com/1019307.
+const unsigned int kBitstreamBufferReadyTimeoutMs =
+    10 * base::Time::kMillisecondsPerSecond;
 
 // The syntax of multiple test streams is:
 //  test-stream1;test-stream2;test-stream3