[pdf] Use implementation_deps for external deps

The pdf generation code depends on zlib and harfbuzz for implementation
reasons and does not re-export them or their headers. Using
implementation_deps means that the `includes` that these targets export
will not be exported to all dependents of the pdf targets.

Change-Id: Ie862a868b2e7cab3bb54e55d0f6d325fc55b60ff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1140917
Auto-Submit: Ben Wagner <bungeman@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Kaylee Lubick <kjlubick@google.com>

src/pdf/BUILD.bazel

diff --git a/src/pdf/BUILD.bazel b/src/pdf/BUILD.bazel
index f65e718..e196715 100644
--- a/src/pdf/BUILD.bazel
+++ b/src/pdf/BUILD.bazel
@@ -70,6 +70,14 @@
         "//include/docs:pdf_hdrs",
     ],
     features = ["layering_check"],
+    implementation_deps = [
+        "@zlib",
+    ] +
+    # We have this harfbuzz dependency all by itself because we need to turn this into a
+    # select statement when rolling into G3.
+    [
+        "@harfbuzz",
+    ],
     local_defines = ["SK_PDF_USE_HARFBUZZ_SUBSET"],
     visibility = ["//:__pkg__"],
     deps = [
@@ -82,14 +90,8 @@
         "//src/utils:clip_stack_utils",
         "//src/utils:float_to_decimal",
         "//modules/skcms",
-        "@zlib",
         # TODO(kjlubick) Remove this dependency after migrating clients
         ":jpeg_helpers",
-    ] +
-    # We have this harfbuzz dependency all by itself because we need to turn this into a
-    # select statement when rolling into G3.
-    [
-        "@harfbuzz",
     ],
 )