Make the I in IFormFiller explicit

BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_common_config") {
   cflags = []
@@ skipping 972 matching lines @@
 static_library("formfiller") {
   sources = [
     "fpdfsdk/formfiller/cba_fontmap.cpp",
     "fpdfsdk/formfiller/cba_fontmap.h",
     "fpdfsdk/formfiller/cffl_checkbox.cpp",
     "fpdfsdk/formfiller/cffl_checkbox.h",
     "fpdfsdk/formfiller/cffl_combobox.cpp",
     "fpdfsdk/formfiller/cffl_combobox.h",
     "fpdfsdk/formfiller/cffl_formfiller.cpp",
     "fpdfsdk/formfiller/cffl_formfiller.h",
-    "fpdfsdk/formfiller/cffl_iformfiller.cpp",
-    "fpdfsdk/formfiller/cffl_iformfiller.h",
+    "fpdfsdk/formfiller/cffl_interactiveformfiller.cpp",
+    "fpdfsdk/formfiller/cffl_interactiveformfiller.h",
     "fpdfsdk/formfiller/cffl_listbox.cpp",
     "fpdfsdk/formfiller/cffl_listbox.h",
     "fpdfsdk/formfiller/cffl_pushbutton.cpp",
     "fpdfsdk/formfiller/cffl_pushbutton.h",
     "fpdfsdk/formfiller/cffl_radiobutton.cpp",
     "fpdfsdk/formfiller/cffl_radiobutton.h",
     "fpdfsdk/formfiller/cffl_textfield.cpp",
     "fpdfsdk/formfiller/cffl_textfield.h",
   ]
   configs += [ ":pdfium_core_config" ]
@@ skipping 751 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }