Leak resources on linux context shutdown if not bound. Closes #3921

* Linux doesn't support rebinding contexts between EGL (Android binding API) and
  GLX (linux) even if no context is bound, so if one platform is used then the
  other we can't bind our child contexts in order to delete objects when a
  context is destroyed.
* We will have to do the same as we do if a different context is bound, and hope
  that the driver tidies this stuff up for us when the context is deleted.

renderdoc/driver/gl/egl_platform.cpp

@@ -60,6 +60,8 @@ class EGLPlatform : public GLPlatform
   RDCDriver m_API = RDCDriver::OpenGLES;
   bool m_Debug = false;
 
+  bool CanFreshBindOnDeletion() { return false; }
+
   bool MakeContextCurrent(GLWindowingData data)
   {
     if(EGL.MakeCurrent)

renderdoc/driver/gl/gl_common.h

@@ -304,6 +304,8 @@ struct GLPlatform
   virtual GLWindowingData MakeOutputWindow(WindowingData window, bool depth,
                                            GLWindowingData share_context) = 0;
 
+  virtual bool CanFreshBindOnDeletion() { return true; }
+
   // for pushing and popping a child context. The default implementation just does
   // MakeContextCurrent but platforms can override this if they need more complex state handling
   virtual bool PushChildContext(GLWindowingData existing, GLWindowingData newChild,

renderdoc/driver/gl/gl_driver.cpp

@@ -1136,7 +1136,7 @@ void WrappedOpenGL::DeleteContext(void *contextHandle)
 
   GLWindowingData savedContext;
 
-  if(existing.ctx == NULL)
+  if(existing.ctx == NULL && m_Platform.CanFreshBindOnDeletion())
   {
     if(m_Platform.PushChildContext(existing, ctxdata.shareGroup->m_BackDoor, &savedContext))
     {

renderdoc/driver/gl/glx_platform.cpp

@@ -53,6 +53,8 @@ class GLXPlatform : public GLPlatform
   RDCDriver m_API = RDCDriver::OpenGL;
   bool m_Debug = false;
 
+  bool CanFreshBindOnDeletion() { return false; }
+
   bool MakeContextCurrent(GLWindowingData data)
   {
     if(GLX.glXMakeCurrent)