Enable fire-and-forget Destroy of HW video decoder, and misc other improvements.

ppapi/cpp/dev/video_decoder_dev.cc

Index: ppapi/cpp/dev/video_decoder_dev.cc
diff --git a/ppapi/cpp/dev/video_decoder_dev.cc b/ppapi/cpp/dev/video_decoder_dev.cc
index 89fe6aead54aa527c78d3eff71328bc83c6e6795..2ef19fcc1ab630fd66cff485750c533ccfda53d7 100644
--- a/ppapi/cpp/dev/video_decoder_dev.cc
+++ b/ppapi/cpp/dev/video_decoder_dev.cc
@@ -32,7 +32,10 @@ VideoDecoder_Dev::VideoDecoder_Dev(const Instance& instance) {
 VideoDecoder_Dev::VideoDecoder_Dev(PP_Resource resource) : Resource(resource) {
 }
 
-VideoDecoder_Dev::~VideoDecoder_Dev() {}
+VideoDecoder_Dev::~VideoDecoder_Dev() {
+  get_interface<PPB_VideoDecoder_Dev>()->Destroy(pp_resource());
+}
+
 
 int32_t VideoDecoder_Dev::Initialize(const PP_VideoConfigElement* config,
                                      const Context3D_Dev& context,
@@ -82,11 +85,4 @@ int32_t VideoDecoder_Dev::Reset(CompletionCallback callback) {
       pp_resource(), callback.pp_completion_callback());
 }
 
-int32_t VideoDecoder_Dev::Destroy(CompletionCallback callback) {
-  if (!has_interface<PPB_VideoDecoder_Dev>())
-    return callback.MayForce(PP_ERROR_NOINTERFACE);
-  return get_interface<PPB_VideoDecoder_Dev>()->Destroy(
-      pp_resource(), callback.pp_completion_callback());
-}
-
 }  // namespace pp