Allow use of Abseil in //net/third_party/quiche.

This has been previously blocked on https://bugs.chromium.org/p/chromium/issues/detail?id=1046390.

Change-Id: I1c0d68dc56d109be6189df0cfb8fc04230949a1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302721
Commit-Queue: Victor Vasiliev <vasilvv@chromium.org>
Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791073}

net/BUILD.gn

@@ -1755,6 +1755,7 @@ source_set("net_public_deps") {
     "//crypto:platform",
     "//net/third_party/quiche:net_quic_proto",
     "//net/third_party/quiche:net_quic_test_tools_proto",
+    "//net/third_party/quiche:quiche_public_deps",
     "//net/traffic_annotation",
     "//third_party/boringssl",
     "//url",

net/third_party/quiche/BUILD.gn

@@ -5,6 +5,16 @@
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
+# Since //net and //net/third_party/quiche have a circular dependency on each
+# other, exporting dependencies from the :quiche target directly does not work.
+# Thus, all public dependencies for QUICHE should go into the target below,
+# which is in turn propagated to all of //net source sets.
+source_set("quiche_public_deps") {
+  visibility = [ "//net:net_public_deps" ]
+
+  public_deps = [ "//third_party/abseil-cpp:absl" ]
+}
+
 source_set("quiche") {
   sources = [
     "src/quic/core/quic_error_codes.cc",

third_party/abseil-cpp/absl.gni

@@ -35,6 +35,7 @@ declare_args() {
 
 _chromium_absl_clients = [
   "//chrome/services/sharing/nearby/platform_v2/*",
+  "//net/third_party/quiche/*",
   "//third_party/blink/renderer/modules/peerconnection",
   "//third_party/blink/renderer/platform",
   "//third_party/googletest:gtest",