Split pdfium_unittests sources.

Move foo_unittest.cpp to the same BUILD.gn file as foo.cpp.
Set up dependencies to make pdfium_unittests pass gn check.

Change-Id: Id9f649d5d0c76fe4254f3887778516abb75fcbce
Reviewed-on: https://pdfium-review.googlesource.com/c/43995
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/BUILD.gn b/fpdfsdk/BUILD.gn
index bf80636..3799d35 100644
--- a/fpdfsdk/BUILD.gn
+++ b/fpdfsdk/BUILD.gn
@@ -4,6 +4,7 @@
 
 import("//build/config/jumbo.gni")
 import("../pdfium.gni")
+import("../testing/test.gni")
 
 jumbo_source_set("fpdfsdk") {
   sources = [
@@ -88,3 +89,19 @@
     allow_circular_includes_from += [ "fpdfxfa" ]
   }
 }
+
+pdfium_unittest_source_set("unittests") {
+  sources = [
+    "fpdf_catalog_unittest.cpp",
+    "fpdf_doc_unittest.cpp",
+    "fpdf_editimg_unittest.cpp",
+  ]
+  deps = [
+    ":fpdfsdk",
+    "../:pdfium_public_headers",
+    "../core/fpdfapi",
+    "../core/fpdfapi/parser",
+    "../core/fpdfdoc",
+  ]
+  pdfium_root_dir = "../"
+}