Static assert bounds of PP_TextRenderingMode and FPDF_TEXT_RENDERMODE

PDFium's FPDFText_GetTextRenderMode() is technically an experimental
API, but it guarantees to return enum values within a certain range. By
statically asserting the bounds of FPDF_TEXT_RENDERMODE, we can simply
DCHECK the returned value of FPDFText_GetTextRenderMode() against those
bounds instead of handling an out-of-bounds value in runtime.

Change-Id: I89d377eeaaab5186712e6b85683bf658590eab53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567452
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833068}

pdf/pdfium/pdfium_assert_matching_enums.cc

@@ -259,6 +259,8 @@ STATIC_ASSERT_ENUM(PP_PRIVATEDUPLEXMODE_SIMPLEX, Simplex);
 STATIC_ASSERT_ENUM(PP_PRIVATEDUPLEXMODE_SHORT_EDGE, DuplexFlipShortEdge);
 STATIC_ASSERT_ENUM(PP_PRIVATEDUPLEXMODE_LONG_EDGE, DuplexFlipLongEdge);
 
+STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_UNKNOWN, FPDF_TEXTRENDERMODE_UNKNOWN);
+STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_FIRST, FPDF_TEXTRENDERMODE_UNKNOWN);
 STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_FILL, FPDF_TEXTRENDERMODE_FILL);
 STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_STROKE, FPDF_TEXTRENDERMODE_STROKE);
 STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_FILLSTROKE,
@@ -272,6 +274,7 @@ STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_STROKECLIP,
 STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_FILLSTROKECLIP,
                    FPDF_TEXTRENDERMODE_FILL_STROKE_CLIP);
 STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_CLIP, FPDF_TEXTRENDERMODE_CLIP);
+STATIC_ASSERT_ENUM(PP_TEXTRENDERINGMODE_LAST, FPDF_TEXTRENDERMODE_LAST);
 
 STATIC_ASSERT_ENUM(chrome_pdf::PDFEngine::FormType::kNone, FORMTYPE_NONE);
 STATIC_ASSERT_ENUM(chrome_pdf::PDFEngine::FormType::kAcroForm,

pdf/pdfium/pdfium_page.cc

@@ -396,12 +396,9 @@ void PDFiumPage::CalculateTextRunStyleInfo(
   }
 
   int render_mode = FPDFText_GetTextRenderMode(text_page, char_index);
-  if (render_mode < PP_TEXTRENDERINGMODE_FIRST ||
-      render_mode > PP_TEXTRENDERINGMODE_LAST) {
-    style_info->render_mode = PP_TEXTRENDERINGMODE_UNKNOWN;
-  } else {
-    style_info->render_mode = static_cast<PP_TextRenderingMode>(render_mode);
-  }
+  DCHECK_GE(render_mode, PP_TEXTRENDERINGMODE_FIRST);
+  DCHECK_LE(render_mode, PP_TEXTRENDERINGMODE_LAST);
+  style_info->render_mode = static_cast<PP_TextRenderingMode>(render_mode);
 }
 
 bool PDFiumPage::AreTextStyleEqual(