Flash: Don't lose a reference to the Graphics3D from the VideoDecoder.

ppapi/shared_impl/ppb_video_decoder_shared.cc

Index: ppapi/shared_impl/ppb_video_decoder_shared.cc
diff --git a/ppapi/shared_impl/ppb_video_decoder_shared.cc b/ppapi/shared_impl/ppb_video_decoder_shared.cc
index ffd422d09979758f42fc6db044c9b1c5540d69d3..7d8d021b5b398156252ac8ac5e121aa58acf78f2 100644
--- a/ppapi/shared_impl/ppb_video_decoder_shared.cc
+++ b/ppapi/shared_impl/ppb_video_decoder_shared.cc
@@ -27,6 +27,8 @@ PPB_VideoDecoder_Shared::PPB_VideoDecoder_Shared(
 }
 
 PPB_VideoDecoder_Shared::~PPB_VideoDecoder_Shared() {
+  // Destroy() must be called before the object is destroyed.
+  DCHECK(graphics_context_ == 0);
 }
 
 thunk::PPB_VideoDecoder_API* PPB_VideoDecoder_Shared::AsPPB_VideoDecoder_API() {
@@ -44,9 +46,12 @@ void PPB_VideoDecoder_Shared::InitCommon(
 }
 
 void PPB_VideoDecoder_Shared::Destroy() {
-  graphics_context_ = 0;
+  if (graphics_context_) {
+    PpapiGlobals::Get()->GetResourceTracker()->ReleaseResource(
+        graphics_context_);
+    graphics_context_ = 0;
+  }
   gles2_impl_ = NULL;
-  PpapiGlobals::Get()->GetResourceTracker()->ReleaseResource(graphics_context_);
 }
 
 bool PPB_VideoDecoder_Shared::SetFlushCallback(