Fix pdfium_test's dependencies for component builds.

One should be able to use component builds with PDFium now. Briefly
mention this in the documentation, and also document why pdfium_test's
build rules are not a good example for others to copy.

Change-Id: Iea9a136940257e29b35e3d21b941343f424f9b93
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/55191
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/README.md b/README.md
index 3e4b9e9..de86081 100644
--- a/README.md
+++ b/README.md
@@ -102,7 +102,7 @@
 pdf_enable_xfa = true  # Set false to remove XFA support (implies JS support).
 pdf_enable_v8 = true  # Set false to remove Javascript support.
 pdf_is_standalone = true  # Set for a non-embedded build.
-is_component_build = false # Disable component build (must be false)
+is_component_build = false # Disable component build (Though it should work)
 
 clang_use_chrome_plugins = false  # Currently must be false.
 ```
diff --git a/samples/BUILD.gn b/samples/BUILD.gn
index f2c8014..bfa34fa 100644
--- a/samples/BUILD.gn
+++ b/samples/BUILD.gn
@@ -43,10 +43,16 @@
     "pdfium_test_write_helper.cc",
     "pdfium_test_write_helper.h",
   ]
+
+  # Note: One should write programs that depend on ../:pdfium. Whereas this
+  # sample program does not set a good example, and depends on PDFium internals,
+  # as well as test support code, for convenience.
   deps = [
-    "../:pdfium",
+    "../:pdfium_public_headers",
+    "../fpdfsdk",
     "../testing/:test_support",
     "../testing/image_diff",
+    "../third_party:pdfium_base",
     "//build/win:default_exe_manifest",
   ]
   configs += [ ":pdfium_samples_config" ]