Rename core/fxcrt IFX files to Iface

This CL renames the 3 IFX files in core/fxcrt to Iface instead.

Change-Id: I7cee6836650b71bc5c5729a8147fda62f0910fe3
Reviewed-on: https://pdfium-review.googlesource.com/27970
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

core/fpdfapi/page/cpdf_image.cpp

diff --git a/core/fpdfapi/page/cpdf_image.cpp b/core/fpdfapi/page/cpdf_image.cpp
index b74de62..68432bf 100644
--- a/core/fpdfapi/page/cpdf_image.cpp
+++ b/core/fpdfapi/page/cpdf_image.cpp
@@ -370,7 +370,7 @@
   return false;
 }
 
-bool CPDF_Image::Continue(IFX_PauseIndicator* pPause) {
+bool CPDF_Image::Continue(PauseIndicatorIface* pPause) {
   RetainPtr<CPDF_DIBSource> pSource = m_pDIBSource.As<CPDF_DIBSource>();
   CPDF_DIBSource::LoadState ret = pSource->ContinueLoadDIBSource(pPause);
   if (ret == CPDF_DIBSource::LoadState::kContinue)