build: add missing pdf resources dep in chromium_src (#52335)

The enable_pdf_viewer block compiles //chrome/browser/pdf sources
(pdf_extension_util.cc, chrome_pdf_stream_delegate.cc, ...) which
include the grit-generated chrome/grit/pdf_resources.h and
chrome/grit/pdf_resources_map.h, but the deps list was missing
//chrome/browser/resources/pdf:resources. Without that dep there is
no ninja ordering edge between those compiles and the resources_grit
action, so cold-object compiles can race header generation and siso
remote builds intermittently fail with
'chrome/grit/pdf_resources_map.h' file not found.

Upstream's chrome/browser/pdf:pdf source_set lists this dep
explicitly; add it here to match.


Claude-Session: https://claude.ai/code/session_01KwFT7AJtQsfGRD3bxFHVNP

Co-authored-by: Claude <noreply@anthropic.com>

chromium_src/BUILD.gn

@@ -391,6 +391,7 @@ static_library("chrome") {
         "//chrome/browser/plugins/pdf_iframe_navigation_throttle.h",
       ]
       deps += [
+        "//chrome/browser/resources/pdf:resources",
         "//components/pdf/browser",
         "//components/pdf/renderer",
         "//components/zoom",