Always initialize CFX_SkiaDeviceDriver::m_bRgbByteOrder

Fix an issue where one of CFX_SkiaDeviceDriver's two ctors forgot to
initialize this member variable. Also mark the variable as const, so
potential missing initializations turn into compile errors.

Bug: 391039185
Change-Id: I9c521ec256937657b6a797ee58b68ea0186d5222
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/128150
Reviewed-by: Thomas Sepez <tsepez@google.com>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index 2431d6c..cebb6e8 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -750,7 +750,7 @@
 }
 
 CFX_SkiaDeviceDriver::CFX_SkiaDeviceDriver(SkCanvas& canvas)
-    : m_pCanvas(&canvas), m_bGroupKnockout(false) {
+    : m_pCanvas(&canvas), m_bRgbByteOrder(false), m_bGroupKnockout(false) {
   int width = m_pCanvas->imageInfo().width();
   int height = m_pCanvas->imageInfo().height();
   DCHECK_EQ(kUnknown_SkColorType, m_pCanvas->imageInfo().colorType());
diff --git a/core/fxge/skia/fx_skia_device.h b/core/fxge/skia/fx_skia_device.h
index aefab25..715e9ba 100644
--- a/core/fxge/skia/fx_skia_device.h
+++ b/core/fxge/skia/fx_skia_device.h
@@ -191,7 +191,7 @@
   sk_sp<SkSurface> surface_;
   UnownedPtr<SkCanvas> m_pCanvas;
   CFX_FillRenderOptions m_FillOptions;
-  bool m_bRgbByteOrder;
+  const bool m_bRgbByteOrder;
   bool m_bGroupKnockout;
 
   CharDetail m_charDetails;