Pepper: Add a nullptr check.

content/renderer/pepper/pepper_plugin_instance_impl.h

Index: content/renderer/pepper/pepper_plugin_instance_impl.h
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.h b/content/renderer/pepper/pepper_plugin_instance_impl.h
index 2ad4318efc701705e3310e60eabdef50e1dbd6ea..b8077857e7f1c0adbd8d0b7f8f957304e825f645 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.h
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.h
@@ -207,6 +207,7 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // Callback when the compositor is finished consuming the committed texture.
   void FinishedConsumingCommittedTexture(
       const cc::TextureMailbox& texture_mailbox,
+      scoped_refptr<PPB_Graphics3D_Impl> graphics_3d,
       const gpu::SyncToken& sync_token,
       bool is_lost);
 
@@ -968,6 +969,9 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // needs to be regenerated.
   cc::TextureMailbox committed_texture_;
 
+  // The Graphics3D that produced the most recently committed texture.
+  scoped_refptr<PPB_Graphics3D_Impl> committed_texture_graphics_3d_;
+
   gpu::SyncToken committed_texture_consumed_sync_token_;
 
   // Holds the number of references |texture_layer_| has to any given