Cache textures in GL GetTexture if they weren't seen before. Refs #386

* When saving the result of a custom shader visualisation, we need to
  get the texture details of a live-created (ie. not from the capture)
  texture.

renderdoc/driver/gl/gl_replay.cpp

@@ -421,6 +421,18 @@ bool GLReplay::IsRenderOutput(ResourceId id)
   return false;
 }
 
+FetchTexture GLReplay::GetTexture(ResourceId id)
+{
+  auto it = m_CachedTextures.find(id);
+  if(it == m_CachedTextures.end())
+  {
+    CacheTexture(id);
+    return m_CachedTextures[id];
+  }
+
+  return it->second;
+}
+
 void GLReplay::CacheTexture(ResourceId id)
 {
   FetchTexture tex;

renderdoc/driver/gl/gl_replay.h

@@ -94,7 +94,7 @@ public:
   FetchBuffer GetBuffer(ResourceId id);
 
   vector<ResourceId> GetTextures();
-  FetchTexture GetTexture(ResourceId id) { return m_CachedTextures[id]; }
+  FetchTexture GetTexture(ResourceId id);
   ShaderReflection *GetShader(ResourceId shader, string entryPoint);
 
   vector<DebugMessage> GetDebugMessages();