Split fsdk_mgr files apart.

This CL separates the CPDFDoc_Environment, CPDFSDK_Document and CPDFSDK_PageView
classes into their own h and cpp files.

Review-Url: https://codereview.chromium.org/2335243002
diff --git a/fpdfsdk/cpdfsdk_interform.cpp b/fpdfsdk/cpdfsdk_interform.cpp
index 1f182d4..f762b89 100644
--- a/fpdfsdk/cpdfsdk_interform.cpp
+++ b/fpdfsdk/cpdfsdk_interform.cpp
@@ -22,11 +22,13 @@
 #include "fpdfsdk/formfiller/cffl_formfiller.h"
 #include "fpdfsdk/fxedit/include/fxet_edit.h"
 #include "fpdfsdk/include/cba_annotiterator.h"
+#include "fpdfsdk/include/cpdfdoc_environment.h"
 #include "fpdfsdk/include/cpdfsdk_annot.h"
+#include "fpdfsdk/include/cpdfsdk_document.h"
+#include "fpdfsdk/include/cpdfsdk_pageview.h"
 #include "fpdfsdk/include/cpdfsdk_widget.h"
 #include "fpdfsdk/include/fsdk_actionhandler.h"
 #include "fpdfsdk/include/fsdk_define.h"
-#include "fpdfsdk/include/fsdk_mgr.h"
 #include "fpdfsdk/include/ipdfsdk_annothandler.h"
 #include "fpdfsdk/javascript/ijs_context.h"
 #include "fpdfsdk/javascript/ijs_runtime.h"