Allocate tile data adaptively to accommodate the frame size increase

If the frame size increases, the tile data buffer needs to be
re-allocated according to the number of tiles existing in current
frame. This patch makes the multi-tile encoding work in spatial
SVC usage case, and partially solved WebM issue 1018.

Change-Id: I1ad6f33058cf5ce6f60ed5024455a709ca80c5ad
diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index 49e8887..7c91da1 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -3785,9 +3785,13 @@
   TOKENEXTRA *pre_tok = cpi->tile_tok[0][0];
   int tile_tok = 0;
 
-  if (cpi->tile_data == NULL) {
+  if (cpi->tile_data == NULL || cpi->allocated_tiles < tile_cols * tile_rows) {
+    if (cpi->tile_data != NULL)
+      vpx_free(cpi->tile_data);
     CHECK_MEM_ERROR(cm, cpi->tile_data,
         vpx_malloc(tile_cols * tile_rows * sizeof(*cpi->tile_data)));
+    cpi->allocated_tiles = tile_cols * tile_rows;
+
     for (tile_row = 0; tile_row < tile_rows; ++tile_row)
       for (tile_col = 0; tile_col < tile_cols; ++tile_col) {
         TileDataEnc *tile_data =
diff --git a/vp9/encoder/vp9_encoder.h b/vp9/encoder/vp9_encoder.h
index 6ce4a67..4d2a186 100644
--- a/vp9/encoder/vp9_encoder.h
+++ b/vp9/encoder/vp9_encoder.h
@@ -306,6 +306,7 @@
   YV12_BUFFER_CONFIG scaled_last_source;
 
   TileDataEnc *tile_data;
+  int allocated_tiles;  // Keep track of memory allocated for tiles.
 
   // For a still frame, this flag is set to 1 to skip partition search.
   int partition_search_skippable_frame;