Bug 1500257 part 6 - Update documentation for RenderFrame and nsDisplayRemote. r=aosmond

The documentation for these pieces are a bit out of date.

Differential Revision: https://phabricator.services.mozilla.com/D17446

--HG--
extra : source : ba62cc27c32f4d8a3fefff8eee5bf47d270130bc
extra : intermediate-source : caafb04b7dd44d607adfa1f5f5cabcd42e367cf4

layout/ipc/RenderFrame.h

@@ -27,6 +27,10 @@ struct TextureFactoryIdentifier;
 
 namespace layout {
 
+/**
+ * RenderFrame connects and manages layer trees for remote frames. It is
+ * directly owned by a TabParent and always lives in the parent process.
+ */
 class RenderFrame final {
   typedef mozilla::layers::CompositorOptions CompositorOptions;
   typedef mozilla::layers::LayerManager LayerManager;
@@ -55,10 +59,10 @@ class RenderFrame final {
   bool IsLayersConnected() const { return mLayersConnected; }
 
  private:
+  // The process id of the remote frame. This is used by the compositor to
+  // do security checks on incoming layer transactions.
   base::ProcessId mTabProcessId;
-  // When our child frame is pushing transactions directly to the
-  // compositor, this is the ID of its layer tree in the compositor's
-  // context.
+  // The layers id of the remote frame.
   LayersId mLayersId;
   // The compositor options for this layers id. This is only meaningful if
   // the compositor actually knows about this layers id (i.e. when
@@ -79,9 +83,8 @@ class RenderFrame final {
 }  // namespace mozilla
 
 /**
- * A DisplayRemote exists solely to graft a child process's shadow
- * layer tree (for a given RenderFrame) into its parent
- * process's layer tree.
+ * A nsDisplayRemote will graft a remote frame's shadow layer tree (for a given
+ * nsFrameLoader) into its parent frame's layer tree.
  */
 class nsDisplayRemote final : public nsDisplayItem {
   typedef mozilla::dom::TabId TabId;