vp8: make mv_min/max thread-local if using partition threading.

Fixes tsan warnings like this in fate-vp8-test-vector-007:

WARNING: ThreadSanitizer: data race (pid=65909)
  Write of size 4 at 0x7d8c0000e088 by thread T1:
    #0 vp8_decode_mb_row_sliced vp8.c:2519 (ffmpeg:x86_64+0x100995ede)
[..]
  Previous write of size 4 at 0x7d8c0000e088 by thread T2:
    #0 vp8_decode_mb_row_sliced vp8.c:2519 (ffmpeg:x86_64+0x100995ede)

1 files changed, 12 insertions, 7 deletions

diff --git a/libavcodec/vp8.h b/libavcodec/vp8.h
index d7e7680276..8263997e3f 100644
--- a/libavcodec/vp8.h
+++ b/libavcodec/vp8.h
@@ -93,6 +93,16 @@ typedef struct VP8Macroblock {
     VP56mv bmv[16];
 } VP8Macroblock;
 
+typedef struct VP8intmv {
+    int x;
+    int y;
+} VP8intmv;
+
+typedef struct VP8mvbounds {
+    VP8intmv mv_min;
+    VP8intmv mv_max;
+} VP8mvbounds;
+
 typedef struct VP8ThreadData {
     DECLARE_ALIGNED(16, int16_t, block)[6][4][16];
     DECLARE_ALIGNED(16, int16_t, block_dc)[16];
@@ -122,6 +132,7 @@ typedef struct VP8ThreadData {
 #define EDGE_EMU_LINESIZE 32
     DECLARE_ALIGNED(16, uint8_t, edge_emu_buffer)[21 * EDGE_EMU_LINESIZE];
     VP8FilterStrength *filter_strength;
+    VP8mvbounds mv_bounds;
 } VP8ThreadData;
 
 typedef struct VP8Frame {
@@ -129,11 +140,6 @@ typedef struct VP8Frame {
     AVBufferRef *seg_map;
 } VP8Frame;
 
-typedef struct VP8intmv {
-    int x;
-    int y;
-} VP8intmv;
-
 #define MAX_THREADS 8
 typedef struct VP8Context {
     VP8ThreadData *thread_data;
@@ -152,8 +158,7 @@ typedef struct VP8Context {
     uint8_t deblock_filter;
     uint8_t mbskip_enabled;
     uint8_t profile;
-    VP8intmv mv_min;
-    VP8intmv mv_max;
+    VP8mvbounds mv_bounds;
 
     int8_t sign_bias[4]; ///< one state [0, 1] per ref frame type
     int ref_count[3];