GpuArcVideoEncodeAccelerator: Initialize bitstream_buffer id to 0

GpuArcVideoEncodeAccelerator doesn't initialize bitstream buffer id. The random
number bitstream buffer id is passed to VEA::UseOutputBitstreamBuffer() at first
and later will pass some middle number as a result of bit operation. Bitstream
buffer id should be initialized by 0. This also set the inital value of
|input_storage_type_| to kShmem.

Bug: None
Test: Confirm bitstream buffer id is 0 in VEA::UseOutputBitstreamBuffer().
Change-Id: I963230439bdd66e66d02d951c1bb38bbd94def94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1623618
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Auto-Submit: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662096}

components/arc/video_accelerator/gpu_arc_video_encode_accelerator.cc

@@ -22,7 +22,10 @@ namespace arc {
 
 GpuArcVideoEncodeAccelerator::GpuArcVideoEncodeAccelerator(
     const gpu::GpuPreferences& gpu_preferences)
-    : gpu_preferences_(gpu_preferences) {}
+    : gpu_preferences_(gpu_preferences),
+      input_storage_type_(
+          media::VideoEncodeAccelerator::Config::StorageType::kShmem),
+      bitstream_buffer_serial_(0) {}
 
 GpuArcVideoEncodeAccelerator::~GpuArcVideoEncodeAccelerator() = default;