Bug 1685183 Part 3: Remove remaining references to PluginInstanceChild. r=jgilbert

These references were left behind in the cleanup of the plugin code.

Depends on D101227

Differential Revision: https://phabricator.services.mozilla.com/D111197

gfx/thebes/gfxPlatform.h

@@ -265,9 +265,8 @@ class gfxPlatform : public mozilla::layers::MemoryPressureListener {
    * aTarget should not keep a reference to the returned surface because that
    * will cause a cycle.
    *
-   * This function is static so that it can be accessed from
-   * PluginInstanceChild (where we can't call gfxPlatform::GetPlatform()
-   * because the prefs service can only be accessed from the main process).
+   * This function is static so that it can be accessed from outside the main
+   * process.
    *
    * aIsPlugin is used to tell the backend that they can optimize this surface
    * specifically because it's used for a plugin. This is mostly for Skia.

ipc/glue/WindowsMessageLoop.cpp

@@ -419,7 +419,6 @@ ProcessOrDeferMessage(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
 
 }  // namespace
 
-// We need the pointer value of this in PluginInstanceChild.
 LRESULT CALLBACK NeuteredWindowProc(HWND hwnd, UINT uMsg, WPARAM wParam,
                                     LPARAM lParam) {
   WNDPROC oldWndProc = (WNDPROC)GetProp(hwnd, kOldWndProcProp);

widget/TextEvents.h

@@ -57,9 +57,6 @@ namespace dom {
 class PBrowserParent;
 class PBrowserChild;
 }  // namespace dom
-namespace plugins {
-class PPluginInstanceChild;
-}  // namespace plugins
 
 enum class AccessKeyType {
   // Handle access key for chrome.