Create a feature flag for PDF portfolio

Creates a feature flag `pdf-portfolio` which will be an indicator that
portfolio feature is enabled in the PDF viewer. Currently this flag is
a dummy flag that has not been linked to the actual feature yet.

Bug: 177188
Change-Id: Ief14cbdad785bad405bf402d3cb57b22314a07c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4651500
Reviewed-by: Lei Zhang <[email protected]>
Commit-Queue: Nigi <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1164297}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 6db2aec..1e0b969 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -40,6 +40,9 @@
 const char kAccessiblePDFFormDescription[] =
     "Enables accessibility support for PDF forms.";
 
+const char kPdfPortfolioName[] = "PDF portfolio";
+const char kPdfPortfolioDescription[] = "Enable PDF portfolio feature.";
+
 const char kPdfUseSkiaRendererName[] =
     "Use Skia Renderer. This flag will have no effect if the renderer choice "
     "is controlled by an enterprise policy.";