vp10: add extern "C" to headers

Change-Id: Ie2e8b37fa01ce8d6b993684f431f3159d511cfb1
diff --git a/vp10/encoder/context_tree.h b/vp10/encoder/context_tree.h
index 9310d1f..67a07cb 100644
--- a/vp10/encoder/context_tree.h
+++ b/vp10/encoder/context_tree.h
@@ -14,6 +14,10 @@
 #include "vp10/common/blockd.h"
 #include "vp10/encoder/block.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct VP10_COMP;
 struct VP10Common;
 struct ThreadData;
@@ -84,4 +88,8 @@
 void vp10_setup_pc_tree(struct VP10Common *cm, struct ThreadData *td);
 void vp10_free_pc_tree(struct ThreadData *td);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif /* VP10_ENCODER_CONTEXT_TREE_H_ */
diff --git a/vp10/encoder/ethread.h b/vp10/encoder/ethread.h
index 997df0d..d72816cd 100644
--- a/vp10/encoder/ethread.h
+++ b/vp10/encoder/ethread.h
@@ -11,6 +11,10 @@
 #ifndef VP10_ENCODER_ETHREAD_H_
 #define VP10_ENCODER_ETHREAD_H_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct VP10_COMP;
 struct ThreadData;
 
@@ -22,4 +26,8 @@
 
 void vp10_encode_tiles_mt(struct VP10_COMP *cpi);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  // VP10_ENCODER_ETHREAD_H_
diff --git a/vp10/encoder/resize.h b/vp10/encoder/resize.h
index 131fc80..bf63770 100644
--- a/vp10/encoder/resize.h
+++ b/vp10/encoder/resize.h
@@ -14,6 +14,10 @@
 #include <stdio.h>
 #include "vpx/vpx_integer.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void vp10_resize_plane(const uint8_t *const input,
                       int height,
                       int width,
@@ -121,4 +125,9 @@
                                 int owidth,
                                 int bd);
 #endif    // CONFIG_VP9_HIGHBITDEPTH
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif    // VP10_ENCODER_RESIZE_H_