components: Cleanup class/struct fwd declarations

components/pdf/renderer/pepper_pdf_host.h

Index: components/pdf/renderer/pepper_pdf_host.h
diff --git a/components/pdf/renderer/pepper_pdf_host.h b/components/pdf/renderer/pepper_pdf_host.h
index 5e838c9e34b66f0bc521300d4639df97b2834380..94e8cc6c25108d9e7d48dfbb928875b10c703e29 100644
--- a/components/pdf/renderer/pepper_pdf_host.h
+++ b/components/pdf/renderer/pepper_pdf_host.h
@@ -20,19 +20,12 @@
 #include "ppapi/host/resource_host.h"
 #include "ppapi/proxy/serialized_structs.h"
 
-struct PP_ImageDataDesc;
-struct PP_Size;
-class SkBitmap;
-
 namespace content {
-class PepperPluginInstance;
 class RenderFrame;
 class RendererPpapiHost;
 }
 
 namespace ppapi {
-class HostResource;
-
 namespace host {
 struct HostMessageContext;
 }  // namespace host