Use default member initializers in CFX_FillRenderOptions

Now that C++20 is available, this now works. Use this as a small test
to see if anything breaks with the switch to C++20.

Bug: pdfium:1932
Change-Id: I9862c6e784f458ff950d3592ffacb4d0a24f7a85
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/112930
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

core/fxge/cfx_fillrenderoptions.h

diff --git a/core/fxge/cfx_fillrenderoptions.h b/core/fxge/cfx_fillrenderoptions.h
index d123f72..e198d83 100644
--- a/core/fxge/cfx_fillrenderoptions.h
+++ b/core/fxge/cfx_fillrenderoptions.h
@@ -33,18 +33,8 @@
   constexpr CFX_FillRenderOptions()
       : CFX_FillRenderOptions(FillType::kNoFill) {}
 
-  // TODO(thestig): Switch to default member initializer for bit-fields when
-  // C++20 is available.
   constexpr explicit CFX_FillRenderOptions(FillType fill_type)
-      : fill_type(fill_type),
-        adjust_stroke(false),
-        aliased_path(false),
-        full_cover(false),
-        rect_aa(false),
-        stroke(false),
-        stroke_text_mode(false),
-        text_mode(false),
-        zero_area(false) {}
+      : fill_type(fill_type) {}
 
   bool operator==(const CFX_FillRenderOptions& other) const {
     return fill_type == other.fill_type &&
@@ -64,28 +54,28 @@
   FillType fill_type;
 
   // Adjusted stroke rendering is enabled.
-  bool adjust_stroke : 1;
+  bool adjust_stroke : 1 = false;
 
   // Whether anti aliasing is enabled for path rendering.
-  bool aliased_path : 1;
+  bool aliased_path : 1 = false;
 
   // Fills with the sum of colors from both cover and source.
-  bool full_cover : 1;
+  bool full_cover : 1 = false;
 
   // Rect paths use anti-aliasing.
-  bool rect_aa : 1;
+  bool rect_aa : 1 = false;
 
   // Path is stroke.
-  bool stroke : 1;
+  bool stroke : 1 = false;
 
   // Renders text by filling strokes.
-  bool stroke_text_mode : 1;
+  bool stroke_text_mode : 1 = false;
 
   // Path is text.
-  bool text_mode : 1;
+  bool text_mode : 1 = false;
 
   // Path encloses zero area.
-  bool zero_area : 1;
+  bool zero_area : 1 = false;
 };
 
 #endif  // CORE_FXGE_CFX_FILLRENDEROPTIONS_H_